0001463101-20-000021 | 10-K | XBRL Viewer

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COVER PAGE - USD ($) $ in Billions	12 Months Ended
COVER PAGE - USD ($) $ in Billions	Dec. 31, 2019	Feb. 14, 2020	Jun. 30, 2019
Cover page.
Document Type	10-K
Document Period End Date	Dec. 31, 2019
Document Annual Report	true
Document Transition Report	false
Entity File Number	001-35480
Entity Registrant Name	Enphase Energy, Inc.
Entity Incorporation, State	DE
Entity Tax Identification Number	20-4645388
Entity Address, Address Line One	47281 Bayside Parkway
Entity Address, City or Town	Fremont
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94538
City Area Code	707
Local Phone Number	774-7000
Title of 12(b) Security	Common Stock, $0.00001 par value per share
Trading Symbol	ENPH
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 1.6
Entity Common Stock, Shares Outstanding		123,179,271
Documents Incorporated by Reference	Portions of the registrant’s Proxy Statement for the 2020 Annual Meeting of Stockholders to be filed with the Securities and Exchange Commission within 120 days after the end of the registrant’s fiscal year ended December 31, 2019 are incorporated by reference into Part III of this Annual Report on Form 10-K.
Entity Central Index Key	0001463101
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Current Fiscal Year End	--12-31

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 251,409	$ 106,237
Restricted cash	44,700	0
Accounts receivable, net of allowances of $564 and $2,138 at December 31, 2019 and December 31, 2018, respectively	145,413	78,938
Inventory	32,056	16,267
Prepaid expenses and other assets	26,079	20,860
Total current assets	499,657	222,302
Property and equipment, net	28,936	20,998
Operating lease, right of use asset	10,117
Intangible assets, net	30,579	35,306
Goodwill	24,783	24,783
Other assets	44,620	36,548
Deferred tax assets, net	74,531	0
Total assets	713,223	339,937
Current liabilities:
Accounts payable	57,474	48,794
Accrued liabilities	47,092	29,010
Deferred revenues, current	81,783	33,119
Warranty obligations, current (includes $6,794 and $4,288 measured at fair value at December 31, 2019 and December 31, 2018, respectively)	10,078	8,083
Debt, current	2,884	28,155
Total current liabilities	199,311	147,161
Long-term liabilities:
Deferred revenues, noncurrent	100,204	76,911
Warranty obligations, noncurrent (includes $13,012 and $7,469 measured at fair value at December 31, 2019 and December 31, 2018, respectively)	27,020	23,211
Other liabilities	11,817	3,250
Debt, noncurrent	102,659	81,628
Total liabilities	441,011	332,161
Commitments and contingent liabilities (Note 12)
Stockholders’ equity:
Common stock, $0.00001 par value, 150,000 shares and 150,000 shares authorized; and 123,109 shares and 107,035 shares issued and outstanding at December 31, 2019 and December 31, 2018, respectively	1	1
Additional paid-in capital	458,315	353,335
Accumulated deficit	(185,181)	(346,302)
Accumulated other comprehensive income (loss)	(923)	742
Total stockholders’ equity	272,212	7,776
Total liabilities and stockholders’ equity	$ 713,223	$ 339,937

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Allowances, accounts receivable	$ 564	$ 2,138
Warranty obligations, current at fair value	6,794	4,288
Warranty obligations, non-current at fair value	$ 13,012	$ 7,469
Common stock, par value (in usd per share)	$ 0.00001	$ 0.00001
Common stock, shares authorized (in shares)	150,000,000	150,000,000
Common stock, shares issued (in shares)	123,109,000	107,035,000
Common stock, shares outstanding (in shares)	123,109,000	107,035,000

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Net revenues	$ 624,333	$ 316,159	$ 286,166
Cost of revenues	403,088	221,714	230,123
Gross profit	221,245	94,445	56,043
Operating expenses:
Research and development	40,381	32,587	33,157
Sales and marketing	36,728	27,047	23,126
General and administrative	38,808	29,086	22,221
Restructuring charges	2,599	4,129	16,917
Total operating expenses	118,516	92,849	95,421
Income (loss) from operations	102,729	1,596	(39,378)
Other expense, net
Interest income	2,513	1,058	276
Interest expense	(9,691)	(10,693)	(8,212)
Other (expense) income, net	(5,437)	(2,190)	1,973
Total other expense, net	(12,615)	(11,825)	(5,963)
Income (loss) before income taxes	90,114	(10,229)	(45,341)
Income tax benefit (provision)	71,034	(1,398)	149
Net income (loss)	$ 161,148	$ (11,627)	$ (45,192)
Net income (loss) per share:
Basic (in USD per share)	$ 1.38	$ (0.12)	$ (0.54)
Diluted (in USD per share)	$ 1.23	$ (0.12)	$ (0.54)
Shares used in per share calculation:
Basic (in shares)	116,713	99,619	82,939
Diluted (in shares)	131,644	99,619	82,939

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 161,148	$ (11,627)	$ (45,192)
Other comprehensive income (loss):
Foreign currency translation adjustments	(1,665)	1,398	(364)
Comprehensive income (loss)	$ 159,483	$ (10,229)	$ (45,556)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Income (Deficit)	Accumulated Other Comprehensive Income (Loss)
Balance, beginning (shares) at Dec. 31, 2016		62,269
Balance, beginning of period at Dec. 31, 2016	$ 1,300	$ 1	$ 252,126	$ (250,535)	$ (292)
Issuance of common stock from exercise of equity awards and employee stock purchase plan (in shares)		1,752
Issuance of common stock from exercise of equity awards and employee stock purchase plan	531		531
Issuance of common stock, net of offering costs (shares)		21,893
Issuance of common stock, net of offering costs	26,425		26,425
Issuance/sale of warrants	1,447		1,447
Stock-based compensation	6,727		6,727
Net income (loss)	(45,192)			(45,192)
Foreign currency translation adjustments	(364)				(364)
Balance, beginning (shares) at Dec. 31, 2017		85,914
Balance, end of period at Dec. 31, 2017	(9,126)	$ 1	287,256	(295,727)	(656)
Issuance of common stock from exercise of equity awards and employee stock purchase plan (in shares)		3,185
Issuance of common stock from exercise of equity awards and employee stock purchase plan	2,806		2,806
Issuance of common stock, net of offering costs (shares)		9,524
Issuance of common stock, net of offering costs	19,766		19,766
Issuance of common stock related to acquisition (shares)		7,500
Issuance of common stock related to acquisition	32,319		32,319
Exercise of warrants (shares)		912
Stock-based compensation	11,188		11,188
Net income (loss)	(11,627)			(11,627)
Foreign currency translation adjustments	1,398				1,398
Balance, beginning (shares) at Dec. 31, 2018		107,035
Balance, end of period at Dec. 31, 2018	7,776	$ 1	353,335	(346,302)	742
Issuance of common stock from exercise of equity awards and employee stock purchase plan (in shares)		5,273
Issuance of common stock from exercise of equity awards and employee stock purchase plan	4,985		4,985
Payment of withholding taxes related to net share settlement of equity awards	(8,198)		(8,198)
Conversion of convertible notes due 2023, net (in shares)		10,801
Conversion of convertible notes due 2023, net	58,857		58,857
Equity component of convertible notes due 2024, net	35,387		35,387
Cost of convertible notes hedge related to the convertible notes due 2024	(36,313)		(36,313)
Issuance/sale of warrants	29,818		29,818
Stock-based compensation	20,417		20,417
Net income (loss)	161,148			161,148
Foreign currency translation adjustments	(1,665)				(1,665)
Balance, beginning (shares) at Dec. 31, 2019		123,109
Balance, end of period at Dec. 31, 2019	$ 272,212	$ 1	$ 458,315	$ (185,181)	$ (923)

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net income (loss)	$ 161,148	$ (11,627)	$ (45,192)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	14,119	9,667	9,004
Provision for doubtful accounts	217	711	476
Asset impairment	1,124	1,601	1,681
Non-cash interest expense	6,081	2,701	1,673
Financing fees on extinguishment of debt	2,152	0	0
Fees paid for repurchase and exchange of convertible notes due 2023	6,000	0	0
Stock-based compensation	20,176	11,432	6,727
Deferred income taxes	(73,375)	123	(1,394)
Changes in operating assets and liabilities:
Accounts receivable	(68,745)	(13,515)	(4,803)
Inventory	(15,789)	9,732	5,961
Prepaid expenses and other assets	(14,293)	(3,130)	(1,227)
Intangible assets	0	(10,000)	0
Accounts payable, accrued and other liabilities	22,200	23,082	(5,078)
Warranty obligations	5,804	1,478	(1,598)
Deferred revenues	72,248	(6,123)	5,328
Net cash provided by (used in) operating activities	139,067	16,132	(28,442)
Cash flows from investing activities:
Purchases of property and equipment	(14,788)	(4,151)	(4,121)
Acquisition	0	(15,000)	0
Net cash used in investing activities	(14,788)	(19,151)	(4,121)
Cash flows from financing activities:
Issuance of convertible notes due 2024, net of issuance costs	127,413	0	0
Purchase of convertible note hedges	(36,313)	0	0
Sale of warrants	29,818	0	0
Fees paid for repurchase and exchange of convertible notes due 2023	(6,000)	0	0
Principal payments and financing fees on debt	(45,855)	(9,976)	0
Proceeds from issuance of common stock, net of issuance costs	0	19,766	26,425
Proceeds from debt, net of issuance costs	0	68,024	26,442
Payments under revolving credit facility	0	0	(10,100)
Proceeds from exercise of equity awards and employee stock purchase plan	4,985	2,800	530
Payment of withholding taxes related to net share settlement of equity awards	(8,198)	0	0
Net cash provided by financing activities	65,850	80,614	43,297
Effect of exchange rate changes on cash and cash equivalents	(257)	(502)	646
Net increase in cash, cash equivalents, and restricted cash	189,872	77,093	11,380
Cash, cash equivalents and restricted cash—Beginning of period	106,237	29,144	17,764
Cash, cash equivalents and restricted cash—End of period	296,109	106,237	29,144
Reconciliation of cash, cash equivalents, and restricted cash to the consolidated balance sheets
Total cash, cash equivalents, and restricted cash	296,109	29,144	17,764
Supplemental cash flow disclosure:
Cash paid for interest	2,689	6,343	5,816
Cash paid for income taxes	1,755	775	909
Supplemental disclosures of non-cash investing and financing activities:
Acquisition funded by issuance of common stock	0	19,219	0
Purchases of fixed assets included in accounts payable	672	895	551
Accrued interest payable unpaid upon exchange of convertible notes due 2023	$ 833	$ 0	$ 0

DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION	12 Months Ended
DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION	DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION Description of Business Enphase Energy, Inc. (the “Company”) is a global energy technology company. The Company delivers smart, easy-to-use solutions that manage solar generation, storage and communication on one intelligent platform. The Company revolutionized the solar industry with its microinverter technology and produces a fully integrated solar-plus-storage solution. Basis of Presentation and Consolidation The accompanying consolidated financial statements are presented in accordance with accounting principles generally accepted in the United States (“U.S.”), or GAAP. The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of income and expenses during the reporting period. Significant estimates and assumptions reflected in the financial statements include revenue recognition, inventory valuation, accrued warranty obligations, incremental borrowing rate for right-of-use assets and lease liability, and tax valuation allowance. These estimates are based on information available as of the date of the financial statements; therefore, actual results could differ materially from management’s estimates using different assumptions or under different conditions.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Revenue Recognition

The Company generates revenue from sales of its solutions, which include microinverter units and related accessories, an Envoy communications gateway, the cloud-based Enlighten monitoring service, and AC Battery storage solutions to distributors, large installers, original equipment manufacturers (“OEMs”) and strategic partners.

On January 1, 2018, the Company adopted Accounting Standards Codification (“ASC”) No. 606, “Revenue Recognition” (“ASC 606” or “Topic 606”) and applied the modified retrospective method to all contracts that were not completed as of January 1, 2018. The most significant impacts upon adoption of Topic 606 were how the Company accounts for revenue related to its Envoy™ communications device and related Enphase Enlighten Software™, or Enlighten, service and the timing of when certain sales incentives are recognized. The full consideration for these products represents a single performance obligation and is deferred and recognized over the estimated service period.

Revenues are recognized when control of the promised goods or services are transferred to the Company’s customers in an amount that reflects the consideration that is expected to be received in exchange for those goods or services. The Company generates all of its revenues from contracts with its customers. A description of principal activities from which the Company generates revenues follows.

•

Products Delivered at a Point in Time. The Company sells its products to customers in accordance with the terms of the related customer contracts. The Company generates revenues from sales of its solutions, which include microinverter units and related accessories, an Envoy communications gateway and Enlighten service, communications accessories and AC Battery™ storage solutions to distributors, large installers, OEMs and strategic partners. Microinverter units, microinverter accessories, and AC Battery storage solutions are delivered to customers at a point in time, and the Company recognizes revenue for these products when the Company transfers control of the product to the customer, which is generally upon shipment.

•

Products Delivered Over Time. The sale of an Envoy communications gateway includes the Company’s Enlighten cloud-based monitoring service. The full consideration for these products represents a single performance obligation and is deferred at the sale date and recognized over the estimated service period of 6 years. The Company also sells certain communication accessories that are delivered over time. The revenue from these products is recognized over the related service period, which is typically 5 or 12 years.

The Company previously sold its Envoy communications device to certain customers under a long-term financing arrangement. Under this financing arrangement, the Company nets the unbilled receivables against deferred revenue.

The Company records certain contra revenue promotions as variable consideration and recognizes these promotions at the time the related revenue is recorded.

The Company records upfront contract acquisition costs, such as sales commissions, to be capitalized and amortized over the estimated life of the asset. For contracts that have a duration of less than one year, the Company follows the Topic 606 practical expedient and expenses these costs when incurred. Commissions related to the Company’s sale of monitoring hardware and service are capitalized and amortized over the period of the associated revenue, which is 6 years.

See Note 3. “Revenue Recognition,” for additional information related to revenue recognition.

Cost of Revenues

The Company includes the following in cost of revenues: product costs, warranty, manufacturing personnel and logistics costs, freight costs, inventory write-downs, hosting services costs related to the Company’s Enlighten service offering, and depreciation and amortization of manufacturing test equipment. A description of principal activities from which the Company recognizes cost of revenue is as follows.


•	Products Delivered at a Point in Time. Cost of revenue from these products is recognized when the Company transfers control of the product to the customer, which is generally upon shipment.


•	Products Delivered Over Time. Cost of revenue from these products is recognized over the related service period.

Cash and Cash Equivalents

The Company considers all highly liquid investments, such as certificates of deposit and money market instruments with maturities of twelve months or less at the time of acquisition to be cash equivalents. For all periods presented, its cash balances consist of amounts held in non-interest-bearing and interest-bearing deposits and money market accounts.

Restricted Cash

Restricted cash represents cash held as certificate of deposit collateralized under a letter of credit issued to a customer. The letter of credit is required as a performance security in a face amount equal to the aggregate purchase price of the executed sales agreement. The letter of credit was issued per the terms of the executed sales agreement with a customer for safe harbor prepayment and the Company has collateralized a certificate of deposit under this letter of credit in an amount of $44.7 million, which was reflected as restricted cash on the Company’s consolidated balance sheet as of December 31, 2019.

Fair Value of Financial Instruments

The carrying amounts of the Company’s cash, cash equivalents and restricted cash, accounts receivable, accounts payable and accrued liabilities approximate fair value because of the short maturity of those instruments.

Accounts Receivables and Contract Assets

The Company receives payments from customers based upon contractual billing schedules. Accounts receivable are recorded when the right to consideration becomes unconditional. Contract assets include deferred product costs and commissions associated with the deferred revenue and will be amortized along with the associated revenue.

Allowance for Doubtful Accounts

The Company maintains allowances for doubtful accounts for uncollectible accounts receivable. Management estimates anticipated losses from doubtful accounts based on days past due, collection history and the financial health of customers. The following table sets forth activities in the allowance for doubtful accounts for the periods indicated.



	December 31,
	2019			2018			2017
	(In thousands)
Balance, at beginning of year	$	2,138		$	2,378		$	2,921
Net charges to expenses	217			711			476
Write-offs, net of recoveries	(1,791		)	(951		)	(1,019		)
Balance, at end of year	$	564		$	2,138		$	2,378

Inventory

Inventory is valued at the lower of cost or market. Market is current replacement cost (by purchase or by reproduction, dependent on the type of inventory). In cases where market exceeds net realizable value (i.e., estimated selling price less reasonably predictable costs of completion and disposal), inventories are stated at net realizable value. Market is not considered to be less than net realizable value reduced by an allowance for an approximately normal profit margin. The Company determines cost on a first-in first-out basis. Management assesses the valuation on a quarterly basis and writes down the value for any excess and obsolete inventory based upon expected demand, anticipated sales price, effect of new product introductions, product obsolescence, customer concentrations, product merchantability and other factors. Inventory write-downs are equal to the difference between the cost of inventories and market.

Long-Lived Assets

Property and equipment are stated at cost less accumulated depreciation. Cost includes amounts paid to acquire or construct the asset as well as any expenditure that substantially adds to the value of or significantly extends the useful life of an existing asset. Repair and maintenance costs are expensed as incurred. Depreciation and amortization are computed using the straight-line method over the estimated useful lives of the assets, which range from 3 to 10 years. Leasehold improvements are amortized over the shorter of the lease term or expected useful life of the improvements.

Internal-use software, whether purchased or developed, is capitalized at cost and amortized on a straight-line basis over its estimated useful life. Costs associated with internally developed software are expensed until the point at which the project has reached the development stage. Subsequent additions, modifications or upgrades to internal-use software are capitalized only to the extent that they provide additional functionality. Software maintenance and training costs are expensed in the period in which they are incurred. The capitalization of internal-use software requires judgment in determining when a project has reached the development stage and the period over which the Company expects to benefit from the use of that software.

Property, plant and equipment, including internal-use software, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset (asset group) may not be recoverable. An impairment loss would be recognized when the carrying amount of an asset exceeds the estimated undiscounted future cash flows expected to result from the use of the asset and its eventual disposition. The amount of the impairment loss to be recorded is calculated by the excess of the asset’s carrying value over its fair value. Fair value is generally determined using a discounted cash flow analysis. The Company recorded asset impairment charges for specific assets that were no longer in use of approximately $1.1 million, $1.6 million and $0.8 million for the years ended 2019, 2018 and 2017, respectively. There were no events or changes in circumstances that may indicate the carrying amount of remaining assets is not recoverable.

Business Combinations

Assets acquired and liabilities assumed as part of a business acquisition are generally recorded at their fair value at the date of acquisition. The excess of purchase price over the fair value of assets acquired and liabilities assumed is recorded as goodwill. Determining fair value of identifiable assets, particularly intangibles, and liabilities acquired also requires the Company to make estimates, which are based on all available information and in some cases assumptions with respect to the timing and amount of future revenues and expenses associated with an asset. Accounting for business acquisitions requires the Company to make judgments as to whether a purchase transaction is a multiple element contract, meaning that it includes other transaction components. This judgment and determination affect the amount of consideration paid that is allocable to assets and liabilities acquired in the business purchase transaction.

Goodwill

Goodwill results from the purchase consideration paid in excess of the fair value of the net assets recorded in connection with a business acquisition. Goodwill is not amortized but is assessed for potential impairment at least annually during the fourth quarter of each fiscal year or between annual tests if an event occurs or circumstances change that would indicate the carrying amount may be impaired. Goodwill is tested at the reporting unit level, which the Company has determined to be the same as the entity as a whole (entity level). The Company first performs qualitative assessment to determine whether it is more likely than not that the fair value of our reporting unit is less than its carrying value. If, after assessing the qualitative factors, we determine that it is more likely than not that the fair value of our reporting unit is less than its carrying value, an impairment analysis will be performed.

Qualitative factors include industry and market consideration, overall financial performance, share price trends and market capitalization and Company-specific events. The Company determined, after performing a qualitative review of its reporting unit, that it is more likely than not that the fair value of our reporting unit exceeds its carrying value. Accordingly, there was no indication of impairment in the years ended 2019, 2018 and 2017 and no quantitative goodwill impairment test was performed.

Intangible Assets

Intangible assets include patents and other purchased intangible assets. Intangible assets with finite lives are amortized on a straight-line basis, with estimated useful lives ranging from 3 to 9 years. Indefinite-lived intangible assets are tested for impairment annually and are also tested for impairment between annual tests if an event occurs or circumstances change that would indicate that the carrying amount may be impaired. Intangible assets with finite lives are tested for impairment whenever events or circumstances indicate that the carrying amount of an asset (asset group) may not be recoverable. An impairment loss is recognized when the carrying amount of an asset exceeds the estimated undiscounted cash flows used in determining the fair value of the asset. The amount of the impairment loss to be recorded is calculated by the excess of the asset’s carrying value over its fair value. Fair value is generally determined using a discounted cash flow analysis. There was no impairment of intangible assets in any of the years presented.

Contract Liabilities

Contract liabilities are recorded as deferred revenue on the accompanying consolidated balance sheets and include payments received in advance of performance obligations under the contract and are realized when the associated revenue is recognized under the contract.

Warranty Obligations

Microinverters Sold Through December 31, 2013

The Company’s warranty accrual provides for the replacement of microinverter units that fail during the product’s warranty term (typically 15 years for first and second generation microinverters and up to 25 years for third and fourth generation microinverters). On a quarterly basis, the Company employs a consistent, systematic and rational methodology to assess the adequacy of its warranty liability. This assessment includes updating all key estimates and assumptions for each generation of product, based on historical results, trends and the most current data available as of the filing date. The key estimates and assumptions used in the warranty liability are thoroughly reviewed by management on a quarterly basis. The key estimates used by the Company to estimate its warranty liability are: (1) the number of units expected to fail over time (i.e., failure rate); (2) the number of failed units expected to result in warranty claims over time (i.e., claim rate); and (3) the per unit cost of replacement units, including outbound shipping and limited labor costs, expected to be incurred to replace failed units over time (i.e., replacement cost).

Estimated Failure Rates — The Company’s Quality and Reliability department has primary responsibility to determine the estimated failure rates for each generation of microinverter. To establish initial failure rate estimates for each generation of microinverter, the Company’s quality engineers use a combination of industry standard Mean Time Between Failure (“MTBF”) estimates for individual components contained in its microinverters, third party data collected on similar equipment deployed in outdoor environments similar to those in which the Company’s microinverters are installed, and rigorous long term reliability and accelerated life cycle testing which simulates the service life of the microinverter in a short period of time. As units are deployed into operating environments, the Company continues to monitor product performance through its Enlighten monitoring platform. It typically takes three to nine months between the date of sale and date of end-user installation. Consequently, the Company’s ability to monitor actual failures of units sold similarly lags by three to nine months. When a microinverter fails and is returned, the Company performs diagnostic root cause failure analysis to understand and isolate the underlying mechanism(s) causing the failure. The Company then uses the results of this analysis (combined with the actual, cumulative performance data collected on those units prior to failure through Enlighten) to draw conclusions with respect to how or if the identified failure mechanism(s) will impact the remaining units deployed in the installed base.

Estimated Claim Rates — Warranty claim rate estimates are based upon observed historical trends and assumptions with respect to expected customer behavior over the warranty period. As the vast majority of the Company’s microinverters have been sold to end users for residential applications, the Company believes that warranty claim rates will be affected by changes over time in residential home ownership because the Company expects that subsequent homeowners are less likely to file claims than the homeowners who originally purchase the microinverters.

Estimated Replacement Costs — Three factors are considered in the Company’s analysis of estimated replacement cost: (1) the estimated cost of replacement microinverters; (2) the estimated cost to ship replacement microinverters to end users; and (3) the estimated labor reimbursement expected to be paid to third party installers performing replacement services for the end user. Because the Company’s warranty provides for the replacement of defective microinverters over long periods of time (between 15 and 25 years, depending on the generation of product purchased), the estimated per unit cost of current and future product generations is considered in the estimated replacement cost. Estimated costs to ship replacement units are based on observable, market-based shipping costs paid by the Company to third party freight carriers. The Company has a separate program that allows third-party installers to claim fixed-dollar reimbursements for labor costs they incur to replace failed microinverter units for a limited time from the date of original installation. Included in the Company’s estimated replacement cost is an analysis of the number of fixed-dollar labor reimbursements expected to be claimed by third party installers over the limited offering period.

In addition to the key estimates noted above, the Company also compares actual warranty results to expected results and evaluates any significant differences. Management may make additional adjustments to the warranty provision based on performance trends or other qualitative factors. If actual failure rates, claim rates, or replacement costs differ from the Company’s estimates in future periods, changes to these estimates may be required, resulting in increases or decreases in the Company’s warranty obligations. Such increases or decreases could be material.

Fair Value Option for Microinverters Sold Since January 1, 2014

The Company’s warranty obligations related to microinverters sold since January 1, 2014 provide the Company the right, but not the requirement, to assign its warranty obligations to a third-party. Under ASC 825, “Financial Instruments” (also referred to as “fair value option”), an entity may choose to elect the fair value option for such warranties at the time it first recognizes the eligible item. The Company made an irrevocable election to account for all eligible warranty obligations associated with microinverters sold since January 1, 2014 at fair value. This election was made to reflect the underlying economics of the time value of money for an obligation that will be settled over an extended period of up to 25 years.

The Company estimates the fair value of warranty obligations by calculating the warranty obligations in the same manner as for sales prior to January 1, 2014 and applying an expected present value technique to that result. The expected present value technique, an income approach, converts future amounts into a single current discounted amount. In addition to the key estimates of failure rates, claim rates and replacement costs, the Company used certain inputs that are unobservable and significant to the overall fair value measurement. Such additional assumptions included compensation comprised of a profit element and risk premium required of a market participant to assume the obligation and a discount rate based on the Company’s credit-adjusted risk-free rate. See Note 9. “Fair Value Measurements,” for additional information.

Warranty obligations initially recorded at fair value at the time of sale will be subsequently re-measured to fair value at each reporting date. In addition, the fair value of the liability will be accreted over the corresponding term of the warranty of up to 25 years using the interest method.

Warranty for Other Products

The Company offers a 5‑year warranty for its Envoy communications gateway and a 10‑year warranty on its AC Battery storage solution. The warranties provide the Company with the right, but not the obligation, to assign its warranty obligations to a third-party. As such, warranties for Envoy and AC Battery storage solution products are accounted for under the fair value method of accounting.

Research and Development Costs

The Company expenses research and development costs as incurred. Research and development expense consists primarily of product development personnel costs, including salaries and benefits, stock-based compensation, other professional costs and allocated facilities costs.

Stock-Based Compensation

Share-based payments are required to be recognized in the Company’s consolidated statements of operations based on their fair values and the estimated number of shares expected to vest. The Company measures stock-based compensation expense for all share-based payment awards, including stock options made to employees and directors, based on the estimated fair values on the date of the grant. The fair value of stock options granted is estimated using the Black-Scholes option valuation model. The fair value of restricted stock units granted is determined based on the price of the Company’s common stock on the date of grant. The fair value of non-market‑based performance stock units granted is determined based on the date of grant or when achievement of performance is probable. The fair value of market‑based performance stock units granted is determined using a Monte‑Carlo model based on the date of grant or when achievement of performance is probable.

Stock-based compensation for stock options and restricted stock units (“RSUs”) is recognized on a straight-line basis over the requisite service period. Stock-based compensation for performance stock units (“PSUs”) without market conditions is recognized when the performance condition is probable of being achieved, and then on a graded basis over the requisite service period. Stock-based compensation for PSUs with market conditions is recognized on a straight-line basis over the requisite service period. Additionally, the Company estimates its forfeiture rate annually based on historical experience and revise the estimates of forfeiture in subsequent periods if actual forfeitures differ from those estimates.

Leases

The Company determines if an arrangement is or contains a lease at inception. Operating lease assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments over the lease term.

Operating lease assets and liabilities are recognized based on the present value of the remaining lease payments discounted using the Company’s incremental borrowing rate. Operating lease assets also include initial direct costs incurred and prepaid lease payments, minus any lease incentives. The Company’s lease terms include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense is recognized on a straight-line basis over the lease term.

The Company combines the lease and non-lease components in determining the operating lease assets and liabilities.

Foreign Currency Translation

The Company and most of its subsidiaries use their respective local currency as their functional currency. Accordingly, foreign currency assets and liabilities are translated using exchange rates in effect at the end of the period. Aggregate exchange gains and losses arising from the translation of foreign assets and liabilities are included in accumulated other comprehensive income (loss) in stockholders' equity. Foreign subsidiaries that use the U.S. dollar as their functional currency remeasure monetary assets and liabilities using exchange rates in effect at the end of the period. In addition, transactions that are denominated in non-functional currency are remeasured using exchange rates in effect at the end of the period. Exchange gains and losses arising from the remeasurement of monetary assets and liabilities are included in other income (expense), net in the consolidated statements of operations. Non-monetary assets and liabilities are carried at their historical values.

Comprehensive Income (Loss)

Comprehensive income (loss) consists of two components, net income (loss) and other comprehensive income (loss). Other comprehensive income (loss) refers to gains and losses that are recorded as an element of stockholders’ equity but are excluded from net income (loss). The Company’s other comprehensive income (loss) consists of foreign currency translation adjustments for all periods presented.

Income Taxes

The Company records income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected tax consequences of temporary differences between the tax bases of assets and liabilities for financial reporting purposes and amounts recognized for income tax purposes. In estimating future tax consequences, generally all expected future events other than enactments or changes in the tax law or rates are considered. Valuation allowances are provided when necessary to reduce deferred tax assets to the amount expected to be realized.

The Company assesses the realizability of the deferred tax assets to determine release of valuation allowance as necessary. In the event the Company determines that it is more likely than not that we would be able to realize deferred tax assets in the future in excess of our net recorded amount, an adjustment to the valuation allowance for the deferred tax asset would increase income in the period such determination was made. Likewise, should it be determined that additional amounts of the net deferred tax asset will not be realized in the future, an adjustment to increase the deferred tax asset valuation allowance will be charged to income in the period such determination is made.

The Company operates in various tax jurisdictions and is subject to audit by various tax authorities. The Company follows accounting for uncertainty in income taxes which requires that the tax effects of a position be recognized only if it is “more likely than not” to be sustained based solely on its technical merits as of the reporting date. The Company considers many factors when evaluating and estimating its tax positions and tax benefits, which may require periodic adjustments and which may not accurately anticipate actual outcomes.

Recently Adopted Accounting Pronouncements

In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-02, “Leases (Topic 842).” ASU 2016-02 requires an entity to recognize a right-of-use asset and lease liability for all leases with terms of more than 12 months. The guidance requires lessees to recognize all leases, with certain exceptions, on their balance sheets, whether operating or financing, while continuing to recognize the expenses on their income statements in a manner similar to current practice. The guidance states that a lessee must recognize a lease liability for the obligation to make lease payments and a right-to-use asset for the right to use the underlying asset for the lease term. On January 1, 2019, the Company adopted ASU 2016-02 using the modified retrospective transition option of applying the new standard at the adoption date for all leases with terms greater than 12 months. The Company elected certain practical expedients upon adoption and as such did not reassess the following: 1) whether any expired or existing contracts are or contain leases; 2) lease classification for any expired or existing leases; 3) initial direct costs for any expired or existing leases; 4) whether existing or expired land easements are or contain leases; and 5) regarding the lease term, from a hindsight perspective, whether or not the Company is reasonably certain to exercise the lease options. However, the Company will evaluate new or modified land easements under the new guidance after the commencement date. The Company also elected the practical expedient to not separate lease and non-lease components. The adoption of ASU 2016-02 on January 1, 2019 resulted in an increase in operating leases, right of use asset of $8.4 million, an increase in other liabilities of $6.8 million, an increase in accrued liabilities and other of $1.5 million and a decrease in other assets of $0.1 million on the Company’s consolidated balance sheets with no impact on the Company’s consolidated statements of operations.

In June 2018, the FASB issued ASU 2018-07, “Compensation - Stock Compensation: Improvements to Non-employee Share-Based Payment Accounting.” ASU 2018-07 was issued to provide guidance on share-based payments granted to non-employees in exchange for goods or services used or consumed in an entity’s own operations and supersedes the guidance in ASC 505-50, “Equity-Based Payments to Non-Employees.” ASU 2018-07 aligns much of the guidance on measuring and classifying non-employee awards with that of awards to employees. The Company adopted ASU 2018-07 on January 1, 2019 using the modified retrospective basis. The adopted standard did not have a material impact on the consolidated financial statements.

Recently Issued Accounting Pronouncements Not Yet Effective

In August 2018, the FASB issued ASU 2018-15, “Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract,” to reduce diversity in practice in accounting for the costs of implementing cloud computing arrangements that are service contracts. ASU 2018-15 allows entities to apply the guidance in the ASC 350-40, “Intangibles–Goodwill and Other–Internal-Use Software,” to determine which implementation costs are eligible to be capitalized as assets in a cloud computing arrangement that is considered a service contract. ASU 2018-15 is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. Early adoption is permitted, including adoption in any interim period. Entities have the option to apply the guidance prospectively to all implementation costs incurred after the date of adoption or retrospectively and are required to make certain disclosures in the interim and annual period of adoption. We will adopt the new standard effective January 1, 2020 and do not expect the adoption of this guidance to have a material impact on our consolidated financial statements.

In June 2016, the FASB issued ASU 2016-13, “Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments,” which requires the measurement and recognition of expected credit losses for financial assets held at amortized cost. ASU 2016-13 replaces the existing incurred loss impairment model with a forward-looking expected credit loss model which will result in earlier recognition of credit losses. We will adopt the new standard effective January 1, 2020 and do not expect the adoption of this guidance to have a material impact on our consolidated financial statements.

REVENUE RECOGNITION

12 Months Ended

Dec. 31, 2019

Revenue from Contract with Customer [Abstract]

REVENUE RECOGNITION

Disaggregated Revenue

The Company has one business activity, which is the design, manufacture and sale of solutions for the solar photovoltaic (“PV”) industry. Disaggregated revenue by primary geographical market and timing of revenue recognition for the Company’s single product line are as follows:



	Years Ended December 31,
	2019		2018
	(In thousands)
Primary geographical markets:
United States	$	523,577	$	219,600
International	100,756		96,559
Total	$	624,333	$	316,159

Timing of revenue recognition:
Products delivered at a point in time	$	584,556	$	270,778
Products and services delivered over time	39,777		45,381
Total	$	624,333	$	316,159

Contract Balances

Receivables, and contract assets and contract liabilities from contracts with customers are as follows:



	December 31, 2019		December 31, 2018
	(In thousands)
Receivables	$	145,413	$	78,938
Short-term contract assets (Prepaid expenses and other assets)	15,055		13,516
Long-term contract assets (Other assets)	42,087		34,148
Short-term contract liabilities (Deferred revenues)	81,783		33,119
Long-term contract liabilities (Deferred revenues)	100,204		76,911

Significant changes in the balances of contract assets (prepaid expenses and other assets) during the period are as follows (in thousands):



Contract Assets
Balance on December 31, 2018	$	47,664
Amount recognized	(15,144		)
Increase	24,622
Balance as of December 31, 2019	$	57,142

For the year ended December 31, 2019, contract liabilities include $49.9 million of safe harbor cash prepayments from its customers for products to be delivered in 2020, which represents the amount equal to the aggregate purchase price of the executed sales agreement. Of the $49.9 million, a letter of credit of $44.7 million was issued for the benefit of one customer and the Company has collateralized under the letter of credit a certificate of deposit of $44.7 million.

Significant changes in the balances of contract liabilities (deferred revenues) during the period are as follows (in thousands):



Contract Liabilities
Balance on December 31, 2018	$	110,030
Revenue recognized	(39,777		)
Increase due to billings	61,825
Increase due to safe harbor prepayments	49,909
Balance as of December 31, 2019	$	181,987

Remaining Performance Obligations

Estimated revenue expected to be recognized in future periods related to performance obligations that are unsatisfied or partially unsatisfied at the end of the reporting period are as follows:



	December 31, 2019
	(In thousands)
Fiscal year:
2020	$	81,783
2021	30,665
2022	25,633
2023	19,841
2024	14,650
Thereafter	9,415
Total	$	181,987

Estimated revenue expected to be recognized in fiscal year 2020 of $81.8 million includes $44.5 million of safe harbor prepayments from customers in the fourth quarter of 2019 for product delivery to the customer in the first quarter of 2020. Remaining $5.4 million of safe harbor prepayments from customers in the fourth quarter of 2019 for product delivery to the customer in the first quarter of 2020 relates to the sale of Envoy communications gateway which will be recognized ratably over the service period.

INVENTORY

12 Months Ended

Dec. 31, 2019

Inventory Disclosure [Abstract]

INVENTORY

Inventory consist of the following:



	December 31, 2019		December 31, 2018
	(In thousands)
Raw materials	$	4,197	$	970
Finished goods	27,859		15,297
Total inventory	$	32,056	$	16,267

PROPERTY AND EQUIPMENT, NET

12 Months Ended

Dec. 31, 2019

Property, Plant and Equipment [Abstract]

PROPERTY AND EQUIPMENT, NET

Property and equipment consist of the following:



	Estimated Useful Life	December 31,
	Estimated Useful Life	2019			2018
	(Years)	(In thousands)
Equipment and machinery	3-10	$	48,114		$	43,566
Furniture and fixtures	5-10	2,404			2,239
Computer equipment	3-5	1,698			2,958
Capitalized software costs	3-5	11,656			12,114
Leasehold improvements	3-10	8,713			8,482
Construction in process		8,446			3,536
Total		81,031			72,895
Less accumulated depreciation and amortization		(52,095		)	(51,897		)
Property and equipment, net		$	28,936		$	20,998

Depreciation expense for property and equipment for the years ended December 31, 2019, 2018 and 2017 was $7.3 million, $8.3 million and $8.6 million, respectively.

As of December 31, 2019 and 2018, unamortized capitalized software costs were $0.8 million and $0.7 million, respectively.

GOODWILL AND INTANGIBLE ASSETS

12 Months Ended

Dec. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

GOODWILL AND INTANGIBLE ASSETS

The Company’s goodwill and purchased intangible assets as of December 31, 2019 and December 31, 2018 are as follows:



	December 31, 2019							December 31, 2018
	Gross		Accumulated Amortization			Net		Gross		Accumulated Amortization			Net
	(In thousands)
Goodwill	$	24,783	$	—		$	24,783	$	24,783	$	—		$	24,783

Intangible assets:
Other indefinite-lived intangibles	$	286	$	—		$	286	$	286	$	—		$	286
Intangible assets with finite lives:
Patents and licensed technology	—		—			—		1,665		(1,665		)	—
Developed technology	13,100		(3,093		)	10,007		13,100		(909		)	12,191
Customer relationships	23,100		(2,814		)	20,286		23,100		(271		)	22,829
Total purchased intangible assets	$	36,486	$	(5,907	)	$	30,579	$	38,151	$	(2,845	)	$	35,306

In August 2018, the Company acquired certain finite-lived intangible assets in its acquisition of SunPower Corporation’s (“SunPower”) microinverter business, primarily developed technology and customer relationships pursuant to an Asset Purchase Agreement (“APA”). See Note 20. “Acquisition,” of the notes to consolidated financial statements included in Item 8 of the Company’s 2019 Annual Report on Form 10-K for additional information related to this acquisition.

Amortization expense related to finite-lived intangible assets are as follows:



	Years Ended December 31,
	2019		2018
	(In thousands)
Developed technology, and patents and licensed technology	$	2,184	$	1,409
Customer relationships	2,543		271
Total amortization expense	$	4,727	$	1,680

Amortization of developed technology, patents and licensed technology is recorded to sales and marketing expense. The developed technology acquired from the Company’s acquisition of SunPower’s microinverter business was embedded in the microinverters that SunPower sold to its customers. The Company does not actively use the developed technology acquired from SunPower and holds the developed technology to prevent others from using it. Accordingly, the Company accounts for the developed technology as a defensive intangible asset and amortizes the associated value over a period of six years from the date of acquisition.

The master supply agreement (“MSA”) entered into with SunPower in August 2018 provides the Company with the exclusive right to supply SunPower with module level power electronics for a period of five years, with options for renewals. The exclusivity arrangement extends throughout the term of the MSA, which comprises all of the expected cash flows from the customer relationship intangible asset, and was a condition to, and was an essential part of the acquisition of SunPower’s microinverter business by the Company. As the fair value ascribed to the customer relationship intangible asset represents payments to a customer, the Company amortizes the value of the customer relationship intangible asset as a reduction to revenue using a pattern of economic benefit method over a useful life of nine years.

ACCRUED LIABILITIES

12 Months Ended

Dec. 31, 2019

Payables and Accruals [Abstract]

ACCRUED LIABILITIES

Accrued liabilities consist of the following:



	December 31, 2019		December 31, 2018
	(In thousands)
Salaries, commissions, incentive compensation and benefits	$	5,524	$	4,107
Customer rebates and sales incentives	24,198		8,527
Freight	4,908		7,286
Operating lease liabilities, current	3,170		—
Other	9,292		9,090
Total accrued liabilities	$	47,092	$	29,010

WARRANTY OBLIGATIONS

12 Months Ended

Dec. 31, 2019

Product Warranties Disclosures [Abstract]

WARRANTY OBLIGATIONS

The Company’s warranty activities were as follows:



	Years Ended December 31,
	2019			2018			2017
	(In thousands)
Warranty obligations, beginning of period	$	31,294		$	29,816		$	31,414
Accruals for warranties issued during period	5,244			3,040			3,797
Changes in estimates	8,591			6,515			(732		)
Settlements	(10,881		)	(8,579		)	(7,037		)
Increase due to accretion expense	2,326			1,989			2,053
Other	524			(1,487		)	321
Warranty obligations, end of period	37,098			31,294			29,816
Less: current portion	(10,078		)	(8,083		)	(7,427		)
Noncurrent	$	27,020		$	23,211		$	22,389

The Company began selling its IQ series microinverters in 2017, sales of which totaled approximately 9.6 million units through 2019, and sold approximately 15.7 million units of prior generation microinverters from 2008 through 2019. IQ 7 sales represented 98% of the Company’s total microinverter sales for the year ended December 31, 2019.

Changes in Estimates

On a quarterly basis, the Company uses the best and most complete underlying information available, following a consistent, systematic and rational methodology to determine its warranty obligations. The Company considers all available evidence to assess the reasonableness of all key assumptions underlying its estimated warranty obligations for each generation of microinverter. The changes in estimates discussed below resulted from consideration of new or additional information becoming available and subsequent developments. Changes in estimates included in the table above were comprised of the following:

2019

In 2019, the Company recorded a $5.5 million increase to warranty expense related to cost increases primarily driven by increased U.S. tariffs announced during 2019 for its products manufactured in China. The Company also recorded additional warranty expense of $3.1 million based on continuing analysis of field performance data and diagnostic root-cause failure analysis primarily relating to its second and third generation products, partially offset by improved failure rates for its IQ7 series.

2018

In 2018, the Company recorded a $0.9 million increase to warranty expense related to cost increases primarily for backwards compatibility cables, supply constrained inventory components as well as tariffs. The Company also recorded additional warranty expense of $3.3 million based on continuing analysis of field performance data and diagnostic root-cause failure analysis primarily relating to its second and third generation products. In addition, the Company recorded an increase of $2.1 million related to increased estimated claim rates and an increase to warranty expense of $0.2 million for labor reimbursement costs expected to be paid to third party installers performing replacement services. These increases were partially offset by a $1.5 million reduction to warranty expense, presented as “Other” in the table above, related to changes in the discount rates for fair value accounting.

2017

In 2017, primarily in the fourth quarter, the Company recorded the impact of product-cost reduction initiatives for its sixth generation microinverters, which are backwards compatible with previous microinverter generations and will be used to fulfill future warranty obligations for all microinverter generations in the field. This resulted in a $2.2 million decrease to warranty expense related to estimated future replacement costs. The Company also recorded, primarily in the third quarter, a decrease to warranty expense of $1.9 million for labor reimbursement costs expected to be paid to third party installers performing replacement services for its second‑generation product. In addition, the Company recorded additional warranty expense of $3.9 million based on continuing analysis of field performance data and diagnostic root-cause failure analysis primarily relating to its second‑generation product.

FAIR VALUE MEASUREMENTS

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

FAIR VALUE MEASUREMENTS

The accounting guidance defines fair value as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining the fair value measurements for assets and liabilities recorded at fair value, the Company considers the principal or most advantageous market in which it would transact and considers assumptions that market participants would use when pricing the asset or liability, such as inherent risk, transfer restrictions, and risk of nonperformance.

The fair value hierarchy requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. An asset’s or liability’s categorization within the fair value hierarchy is based upon the lowest level of input that is significant to the fair value measurement. Three levels of inputs may be used to measure fair value:


•	Level 1—Valuations based on quoted prices in active markets for identical assets or liabilities that the Company is able to access. Since valuations are based on quoted prices that are readily and regularly available in an active market, valuation of such assets or liabilities do not entail a significant degree of judgment.


•	Level 2—Valuations based on one or more quoted prices in markets that are not active or for which all significant inputs are observable, either directly or indirectly.


•	Level 3—Valuations based on inputs that are unobservable and significant to the overall fair value measurement.

The following table presents the Company’s liabilities that were measured at fair value on a recurring basis and its categorization within the fair value hierarchy.



	Fair Value Hierarchy	December 31, 2019		December 31, 2018
		(In thousands)
Warranty obligations
Current		$	6,794	$	4,288
Non-current		13,012		7,469
Total warranty obligations measured at fair value	Level 3	$	19,806	$	11,757

Fair Value Option for Warranty Obligations Related to Microinverters Sold Since January 1, 2014

The Company estimates the fair value of warranty obligations by calculating the warranty obligations in the same manner as for sales prior to January 1, 2014 and applying an expected present value technique to that result. The expected present value technique, an income approach, converts future amounts into a single current discounted amount. In addition to the key estimates of failure rates, claim rates and replacement costs, the Company used certain Level 3 inputs which are unobservable and significant to the overall fair value measurement. Such additional assumptions included a discount rate based on the Company’s credit-adjusted risk-free rate and compensation comprised of a profit element and risk premium required of a market participant to assume the obligation.

The following table provides information regarding changes in nonfinancial liabilities related to the Company’s warranty obligations measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the periods indicated.



	Years Ended December 31,
	2019			2018			2017
	(In thousands)
Balance at beginning of period	$	11,757		$	9,791		$	10,332
Accruals for warranties issued during period	5,244			3,040			3,591
Changes in estimates	6,167			2,455			(4,551		)
Settlements	(6,212		)	(4,030		)	(1,956		)
Increase due to accretion expense	2,326			1,989			2,053
Other	524			(1,488		)	322
Balance at end of period	$	19,806		$	11,757		$	9,791

Quantitative and Qualitative Information about Level 3 Fair Value Measurements

As of December 31, 2019 and December 31, 2018, the significant unobservable inputs used in the fair value measurement of the Company’s liabilities designated as Level 3 are as follows:



			Percent Used (Weighted Average)
Item Measured at Fair Value	Valuation Technique	Description of Significant Unobservable Input	December 31, 2019	December 31, 2018
Warranty obligations for microinverters sold since January 1, 2014	Discounted cash flows	Profit element and risk premium	14%	16%
	Discounted cash flows	Credit-adjusted risk-free rate	16%	19%

Sensitivity of Level 3 Inputs - Warranty Obligations

Each of the significant unobservable inputs is independent of the other. The profit element and risk premium are estimated based on requirements of a third-party participant willing to assume the Company’s warranty obligations. The credit‑adjusted risk‑free rate (“discount rate”) is determined by reference to the Company’s own credit standing at the fair value measurement date. Increasing the profit element and risk premium input by 100 basis points would result in a $0.2 million increase to the liability. Decreasing the profit element and risk premium by 100 basis points would result in a $0.2 million reduction of the liability. Increasing the discount rate by 100 basis points would result in a $0.8 million reduction of the liability. Decreasing the discount rate by 100 basis points would result in a $0.9 million increase to the liability.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

RESTRUCTURING

12 Months Ended

Dec. 31, 2019

Restructuring and Related Activities [Abstract]

RESTRUCTURING

Restructuring expense consist of the following:



	Years Ended December 31,
	2019			2018		2017
	(In thousands)
Redundancy and employee severance and benefit arrangements	$	1,575		$	2,228	$	2,827
Asset impairments	1,124			1,601		522
Consultants engaged in restructuring activities	—			—		12,100
Lease loss reserves	(100		)	300		1,468
Total restructuring charges	$	2,599		$	4,129	$	16,917

2018 Plan

In the third quarter of 2018, the Company began implementing restructuring actions (the “2018 Plan”) to lower its operating expenses. The restructuring actions include reorganization of the Company’s global workforce, elimination of certain non-core projects and consolidation of facilities. The Company completed its restructuring activities under the 2018 Plan in 2019.

The following table provides information regarding changes in the Company’s 2018 Plan accrued restructuring balance for the periods indicated.



	Redundancy and Employee Severance and Benefits			Lease Loss Reserves and Contractual Obligations			Total
	(In thousands)
Balance as of December 31, 2018	$	904		$	288		$	1,192
Charges	2,699			—			2,699
Cash payments	(1,610		)	—			(1,610		)
Non-cash settlement and other	(1,993		)	(288		)	(2,281		)
Balance as of December 31, 2019	$	—		$	—		$	—

The following table presents the details of the Company’s restructuring charges under the 2018 Plan for the period indicated:



	Years Ended December 31,
	2019			2018
	(In thousands)
Redundancy and employee severance and benefit arrangements	$	1,575		$	2,228
Asset impairments	1,124			1,636
Lease loss reserves	(100		)	340
Total restructuring charges	$	2,599		$	4,204

2016 Plan

In the third quarter of 2016, the Company began implementing restructuring actions (the “2016 Plan”) to lower its operating expenses. The restructuring actions have included reductions in the Company’s global workforce, the elimination of certain non-core projects, consolidation of office space at the Company’s corporate headquarters and the engagement of management consultants to assist the Company in making organizational and structural changes to improve operational efficiencies and reduce expenses. The Company completed its restructuring activities under the 2016 Plan in 2017.

The following table provides information regarding changes in the Company’s 2016 Plan accrued restructuring balance for the periods indicated.



	Employee Severance and Benefits			Lease Loss Reserves and Contractual Obligations			Total
	(In thousands)
Balance as of December 31, 2017	229			1,094			1,323
Charges and adjustments	—			(40		)	(40		)
Cash payments and receipts, net	(229		)	537			308
Balance as of December 31, 2018	—			$	1,591		1,591
Other ⁽¹⁾	—			(1,591		)	(1,591		)
Balance as of December 31, 2019	$	—		$	—		$	—

(1)

Adoption of ASU 2016-02.

DEBT

12 Months Ended

Dec. 31, 2019

Debt Disclosure [Abstract]

DEBT

The following table provides information regarding the Company’s long-term debt.



	December 31, 2019			December 31, 2018
	(In thousands)
Convertible notes
Notes due 2024	$	132,000		$	—
Less: unamortized discount and issuance costs	(35,815		)	—
Carrying amount of Notes due 2024	96,185			—

Notes due 2023	5,000			65,000
Less: unamortized issuance costs	(143		)	(2,361		)
Carrying amount of Notes due 2023	4,857			62,639

Term loan	—			41,524
Less: unamortized discount and issuance costs	—			(1,059		)
Carrying amount of term loan	—			40,465

Sale of long-term financing receivable recorded as debt	4,501			6,679
Total carrying amount of debt	105,543			109,783
Less: current portion term loan	—			(25,417		)
Less: current portion of long-term financing receivable recorded as debt	(2,884		)	(2,738		)
Long-term debt	$	102,659		$	81,628

Convertible Senior Notes due 2024

On June 5, 2019, the Company issued $132.0 million aggregate principal amount of 1.0% convertible senior notes due 2024 (the “Notes due 2024”). The Notes due 2024 are general unsecured obligations and bear interest at an annual rate of 1.0% per year, payable semi-annually on June 1 and December 1 of each year, beginning December 1, 2019. The Notes due 2024 are governed by an indenture between the Company and U.S. Bank National Association, as trustee. The Notes due 2024 will mature on June 1, 2024, unless earlier repurchased by the Company or converted at the option of the holders. The Company may not redeem the notes prior to the maturity date, and no sinking fund is provided for the notes. The Notes due 2024 may be converted, under certain circumstances as described below, based on an initial conversion rate of 48.7781 shares of common stock per $1,000 principal amount (which represents an initial conversion price of $20.5010 per share). The conversion rate for the Notes due 2024 will be subject to adjustment upon the occurrence of certain specified events but will not be adjusted for accrued and unpaid interest. In addition, upon the occurrence of a make-whole fundamental change (as defined in the relevant indenture), the Company will, in certain circumstances, increase the conversion rate by a number of additional shares for a holder that elects to convert its notes in connection with such make-whole fundamental change. The Company received approximately $128.0 million in net proceeds, after deducting the initial purchasers’ discount, from the issuance of the Notes due 2024.

The Notes due 2024 may be converted on any day prior to the close of business on the business day immediately preceding December 1, 2023, in multiples of $1,000 principal amount, at the option of the holder under any of the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on September 30, 2019 (and only during such calendar quarter), if the last reported sale price of the Company’s common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter is greater than or equal to $26.6513 (130% of the conversion price) on each applicable trading day; (2) during the five business day period after any five consecutive trading day period (the “measurement period”) in which the “trading price” (as defined in the relevant indenture) per $1,000 principal amount of notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of the Company’s common stock and the conversion rate on each such trading day; or (3) upon the occurrence of specified corporate events. On and after December 1, 2023 until the close of business on the second scheduled trading day immediately preceding the maturity date of June 1, 2024, holders may convert their notes at any time, regardless of the foregoing circumstances. Upon the occurrence of a fundamental change (as defined in the relevant indenture), holders may require the Company to repurchase all or a portion of their Notes due 2024 for cash at a price equal to 100% of the principal amount of the notes to be repurchased plus any accrued and unpaid interest to, but excluding, the fundamental change repurchase date.

Upon conversion of any of the notes, the Company will pay or deliver, as the case may be, cash, shares of common stock or a combination of cash and common stock, at the Company’s election.

In accounting for the issuance of the Notes due 2024, on June 5, 2019, the Company separated the Notes due 2024 into liability and equity components. The carrying amount of the liability component of approximately $95.6 million was calculated by using a discount rate of 7.75%, which was the Company’s borrowing rate on the date of the issuance of the notes for a similar debt instrument without the conversion feature. The carrying amount of the equity component of approximately $36.4 million, representing the conversion option, was determined by deducting the fair value of the liability component from the par value of the Notes due 2024. The equity component of the Notes due 2024 is included in additional paid-in capital in the consolidated balance sheet and is not remeasured as long as it continues to meet the conditions for equity classification. The difference between the principal amount of the Notes due 2024 and the liability component (the “debt discount”) is amortized to interest expense using the effective interest method over the term of the Notes due 2024.

The Company separated the Notes due 2024 into liability and equity components, this resulted in a tax basis difference associated with the liability component that represents a temporary difference. The Company recognized the deferred taxes of $0.3 million for the tax effect of that temporary difference as an adjustment to the equity component included in additional paid-in capital in the consolidated balance sheet.

Debt issuance costs for the issuance of the Notes due 2024 were approximately $4.6 million, consisting of initial purchasers' discount and other issuance costs. In accounting for the transaction costs, the Company allocated the total amount incurred to the liability and equity components using the same proportions as the proceeds from the Notes due 2024. Transaction costs attributable to the liability component were approximately $3.3 million, were recorded as debt issuance cost (presented as contra debt in the consolidated balance sheet) and are being amortized to interest expense over the term of the Notes due 2024. The transaction costs attributable to the equity component were approximately $1.3 million and were netted with the equity component in stockholders’ equity. As of December 31, 2019, the unamortized deferred issuance cost for the Notes due 2024 was $2.9 million on the consolidated balance sheet.

The following table presents the total amount of interest cost recognized relating to the Notes due 2024:



	Year Ended December 31, 2019
	(In thousands)
Contractual interest expense	$	759
Amortization of debt discount	3,492
Amortization of debt issuance costs	375
Total interest cost recognized	$	4,626

The effective interest rate on the liability component Notes due 2024 was 7.75% for the years ended December 31, 2019, which remain unchanged from the date of issuance. The remaining unamortized debt discount was $32.9 million as of December 31, 2019, will be amortized over approximately 4.4 years.

The Company carries the Notes due 2024 at face value less unamortized discount and issuance costs on its condensed consolidated balance sheet. The fair value of the Notes due 2024 was determined to be $190.9 million based on the closing trading prices per $100 principal amount as of the last day of trading for the period. The Company considers the fair value of the Notes due 2024 to be a Level 2 measurement as they are not actively traded.

Convertible Note Hedge and Warrant Transactions

In connection with the offering of the Notes due 2024, the Company entered into privately-negotiated convertible note hedge transactions pursuant to which the Company has the option to purchase a total of approximately 6.4 million shares of its common stock (subject to anti-dilution adjustments), which is the same number of shares initially issuable upon conversion of the notes, at a price of $20.5010 per share, which is the initial conversion price of the Notes due 2024. The total cost of the convertible note hedge transactions was approximately $36.3 million. The convertible note hedge transactions are expected generally to reduce potential dilution to the Company’s common stock upon any conversion of the Notes due 2024 and/or offset any cash payments the Company is required to make in excess of the principal amount of converted notes, as the case may be. As of December 31, 2019, the Company had not purchased any shares under the convertible note hedge transactions.

Additionally, the Company separately entered into privately-negotiated warrant transactions (the “Warrants”) whereby the Company sold warrants to acquire approximately 6.4 million shares of the Company’s common stock (subject to anti-dilution adjustments) at an initial strike price of $25.2320 per share. The Company received aggregate proceeds of approximately $29.8 million from the sale of the Warrants. If the market value per share of the Company’s common stock, as measured under the Warrants, exceeds the strike price of the Warrants, the Warrants will have a dilutive effect on the Company’s earnings per share, unless the Company elects, subject to certain conditions, to settle the Warrants in cash. Taken together, the purchase of the convertible note hedges and the sale of the Warrants are intended to reduce potential dilution from the conversion of the Notes due 2024 and to effectively increase the overall conversion price from $20.5010 to $25.2320 per share. The Warrants are only exercisable on the applicable expiration dates in accordance with the Warrants. Subject to the other terms of the Warrants, the first expiration date applicable to the Warrants is September 1, 2024, and the final expiration date applicable to the Warrants is April 22, 2025. As of December 31, 2019, the Warrants had not been exercised and remained outstanding.

Given that the transactions meet certain accounting criteria, the convertible note hedge transactions and the warrants are recorded in stockholders’ equity, and they are not accounted for as derivatives and are not remeasured each reporting period.

Convertible Senior Notes due 2023

In August 2018, the Company sold $65.0 million aggregate principal amount of 4.0% convertible senior notes due 2023 (the “Notes due 2023”) in a private placement. On May 30, 2019, the Company entered into separately and privately negotiated transactions with certain holders of the Notes due 2023 resulting in the repurchase and exchange, as of June 5, 2019, of $60.0 million aggregate principal amount of the notes in consideration for the issuance of 10,801,080 shares of common stock and separate cash payments totaling $6.0 million. As of December 31, 2019, $5.0 million aggregate principal amount of the Notes due 2023 remain outstanding.

The remaining outstanding Notes due 2023 are general unsecured obligations and bear interest at a rate of 4.0% per year, payable semi-annually on February 1 and August 1 of each year. The Notes due 2023 are governed by an indenture between the Company and U.S. Bank National Association, as trustee. The remaining outstanding Notes due 2023 will mature on August 1, 2023, unless earlier repurchased by the Company or converted at the option of the holders. The Company may not redeem the remaining Notes due 2023 prior to the maturity date, and no sinking fund is provided for such notes. The remaining Notes due 2023 are convertible, at a holder’s election, in multiples of $1,000 principal amount, into shares of the Company’s common stock based on the applicable conversion rate. The initial conversion rate for such notes is 180.0180 shares of common stock per $1,000 principal amount of notes (which is equivalent to an initial conversion price of approximately $5.56 per share). The conversion rate and the corresponding conversion price are subject to adjustment upon the occurrence of certain events but will not be adjusted for any accrued and unpaid interest. Holders of the remaining Notes due 2023 who convert their notes in connection with a make-whole fundamental change (as defined in the applicable indenture) are, under certain circumstances, entitled to an increase in the conversion rate. Additionally, in the event of a fundamental change, holders of the remaining Notes due 2023 may require the Company to repurchase all or a portion of their notes at a price equal to 100% of the principal amount of notes, plus any accrued and unpaid interest, including any additional interest to, but excluding, the repurchase date. Holders may convert all or any portion of their Notes due 2023 at their option at any time prior to the close of business on the business day immediately preceding the maturity date, in multiples of $1,000 principal amount.

During the year ended December 31, 2019, the Company recognized $6.0 million inducement cost in other expense, net on the Company’s consolidated statement of operations and reclassed $2.0 million of deferred issuance costs, offset by $0.8 million in accrued interest in additional paid in capital on the Company’s consolidated balance sheet as of December 31, 2019 related to the exchange of $60.0 million aggregate principal amount of the Notes due 2023 consummated by the Company on June 5, 2019.

The following table presents the amount of interest cost recognized relating to the contractual interest coupon and the amortization of debt issuance costs of the Notes due 2023.



	Years Ended December 31,
	2019		2018
	(In thousands)
Contractual interest expense	$	1,226	$	975
Amortization of debt issuance costs	245		193
Total interest costs recognized	$	1,471	$	1,168

Term Loan

In July 2016, the Company entered into a Loan and Security Agreement (the “Original Term Loan Agreement”) with lenders that are affiliates of Tennenbaum Capital Partners, LLC. In February 2017, the Company entered into an Amended and Restated Loan and Security Agreement (the “Loan Agreement”) that amended and restated the Original Term Loan Agreement. The Loan Agreement provided for a $25.0 million secured term loan to the Company (the “New Term Loan”), which is in addition to the $25.0 million secured term loan borrowed by the Company under the Original Term Loan Agreement (together with the “New Term Loan” the “Term Loans”).

On January 28, 2019, the Company repaid in full the remaining principal amount of the Term Loans of approximately $39.5 million plus accrued interest and fees.

Sale of Long-Term Financing Receivables

The Company entered into an agreement with a third party in the fourth quarter of 2017 to sell certain current and future receivables at a discount. In December 2017, the third party made an initial purchase of receivables that resulted in net proceeds to the Company of $2.8 million. This transaction was recorded as debt on the accompanying consolidated balance sheets, and the debt balance was relieved in January 2019 as the underlying receivables were settled. During the year ended December 31, 2018, the third party made three additional purchases of receivables that resulted in total net proceeds to the Company of $5.6 million. These transactions were recorded as debt on the accompanying consolidated balance sheets, and the total associated debt balance will be relieved by September 2021 as the underlying receivables are settled. After the initial purchase, the buyer had the option to purchase certain additional future receivables at various fixed discounts. This option was valued at $0.7 million and was recorded as a liability with a corresponding offset to debt as of December 31, 2017. As of December 31, 2019, all purchases relating to this option had been made, and the liability has been relieved. See Note 9. “Fair Value Measurements,” for additional information.

COMMITMENTS AND CONTINGENT LIABILITIES

12 Months Ended

Dec. 31, 2019

Commitments and Contingencies Disclosure [Abstract]

COMMITMENTS AND CONTINGENT LIABILITIES

Operating Leases

The Company leases office facilities under noncancelable operating leases that expire on various dates through 2028, some of which may include options to extend the leases for up to 12 years.

The components of lease expense are presented as follows:



	Year Ended December 31, 2019
	(In thousands)
Operating lease costs	$	4,041

The components of lease liabilities are presented as follows:



	December 31, 2019
	(In thousands)
Operating lease liabilities, current (Accrued liabilities)	$	3,170
Operating lease liabilities, noncurrent (Other liabilities)	9,542
Total operating lease liabilities	$	12,712

Supplemental lease information:
Weighted average remaining lease term	5.5 years
Weighted average discount rate	8.6%

Supplemental cash flow and other information related to operating leases, are as follows:



	Year Ended December 31, 2019
	(In thousands)
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	3,636

Non-cash investing activities:
Lease liabilities arising from obtaining right-of-use assets	$	4,834

Undiscounted cash flows of operating lease liabilities as of December 31, 2019 are as follows:



	Lease Amounts
	(In thousands)
Year:
2020	$	4,156
2021	4,238
2022	2,927
2023	2,188
2024	921
2025 and thereafter	740
Total lease payments	15,170
Less: imputed lease interest	(2,458		)
Total lease liabilities	$	12,712

As previously disclosed in the Company’s Annual Report on Form 10-K and under the previous lease accounting standard ASC 840, “Leases,” the aggregate future minimum lease payments under the Company’s noncancelable operating leases, as of December 31, 2018, are as follows:



	Lease Amounts
	(In thousands)
Year:
2019	$	3,738
2020	3,532
2021	3,276
2022	1,810
2023	945
Thereafter	1,252
Total	14,553
Sublease income to be recognized in the future under noncancelable subleases	(922		)
Net operating lease minimum payments	$	13,631

Purchase Obligations

The Company has contractual obligations related to component inventory that its primary contract manufacturer procures on its behalf in accordance with its production forecast as well as other inventory related purchase commitments. As of December 31, 2019, these purchase obligations totaled approximately $99.5 million.

Letter of Credits

As of December 31, 2019, we had a standby letter of credit in the aggregate amount of $44.7 million, primarily in connection with one of our customer contracts. The letter of credit serves as a performance security for product delivery to the customer in 2020 and will expire April 30, 2020. The Company has collateralized under the letter of credit a certificate of deposit of $44.7 million. No amounts have been drawn against this letter of credit. Further information relating to the letter of credit may be found in Note 3, “Revenue Recognition,” of the notes to consolidated financial statements included in Part II, Item 8 of this Annual Report on Form 10-K.

Litigation

From time-to-time, the Company may be involved in litigation relating to claims arising out of its operations. The Company is not currently involved in any material legal proceedings; however, the Company may be involved in material legal proceedings in the future. Such matters are subject to uncertainty and there can be no assurance that such legal proceedings will not have a material effect on its business, results of operations, financial position or cash flows.

SALE OF COMMON STOCK	12 Months Ended
SALE OF COMMON STOCK	Dec. 31, 2019
Equity [Abstract]
SALE OF COMMON STOCK	SALE OF COMMON STOCK In February 2018, the Company entered into a Securities Purchase Agreement with an investor pursuant to which the Company, in a private placement, issued and sold to the investor 9.5 million shares of the Company’s common stock at a price per share of $2.10, for gross proceeds of $20.0 million. In January 2017, the Company completed a private placement of securities that resulted in the issuance of approximately 10.8 million shares of common stock and gross proceeds of $10.0 million.

STOCK-BASED COMPENSATION

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

STOCK-BASED COMPENSATION

Description of Equity Incentive Plans

2006 Plan

Under the Company’s 2006 Equity Incentive Plan (the “2006 Plan”), equity awards granted generally vest over a 4‑year period from the date of grant with a contractual term of up to 10 years. As of December 31, 2019, there were less than 0.1 million shares of options outstanding under the 2006 Plan. No further stock options or other stock awards may be granted under the 2006 Plan.

2011 Plan

Under the 2011 Equity Incentive Plan (the “2011 Plan”), the Company could initially issue up to 2,643,171 shares of its common stock pursuant to stock options, stock appreciation rights (“SARS”), restricted stock awards (“RSA”), RSUs, PSUs, and other forms of equity compensation, or collectively, stock awards, all of which may be granted to employees, including officers, and to non-employee directors and consultants. Options granted under the 2011 Plan before August 1, 2012 generally expire 10 years after the grant date and options granted thereafter generally expire 7 years after the grant date. Equity awards granted under the 2011 Plan generally vest over a 4-year period from the date of grant based on continued employment. The number of shares of the Company’s common stock authorized for issuance under the 2011 Plan automatically increases on each January 1 by 4.5% of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year, or such lesser number of shares of common stock as determined by the board of directors. As of December 31, 2019, 4,355,838 shares remained available for issuance pursuant to future grants under the 2011 Plan. On January 1, 2020, the shares available for issuance under the 2011 Plan automatically increased by 5,539,886 shares.

2011 Employee Stock Purchase Plan

The 2011 Employee Stock Purchase Plan (“ESPP”) became effective immediately upon the execution and delivery of the underwriting agreement for the Company’s initial public offering on March 29, 2012. The ESPP authorized the issuance of 669,603 shares of the Company’s common stock pursuant to purchase rights granted to employees. The number of shares of common stock reserved for issuance will automatically increase, on each January 1, by a lesser of (i) 330,396 shares of the Company’s common stock or (ii) 1.0% of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year, as determined by the Company’s board of directors. At the Annual Meeting of Stockholders held on May 18, 2017 the Company’s stockholders approved a one-time amendment to the Company’s ESPP to increase the aggregate number of shares available for purchase by 400,000 shares and to increase the annual automatic minimum increase in shares reserved for issuance from 330,396 to 700,000 shares effective January 1, 2018. As of December 31, 2019, 936,020 shares remained available for future issuance under the ESPP. On January 1, 2020, the shares available for issuance under the ESPP automatically increased by 700,000 shares.

The ESPP is implemented by concurrent offering periods and each offering period may contain up to four interim purchase periods. In general, offering periods consists of the 24-month periods commencing on each May 15 and November 15 of a calendar year.

Generally, all full-time employees, including executive officers, are eligible to participate in the ESPP. The ESPP permits eligible employees to purchase the Company’s common stock through payroll deductions, which may not exceed 15% of the employee’s total compensation subject to certain limits. Stock may be purchased under the plan at a price equal to 85% of the fair market value of the Company’s stock on either the date of purchase or the first day of an offering period, whichever is lower. A two‑year look-back feature in the Company’s ESPP causes an offering period to reset if the fair value of the Company’s common stock on a purchase date is less than that on the initial offering date for that offering period. The reset feature, when triggered, will be accounted for as a modification to the original offering, resulting in additional expense to be recognized over the 24-month period of the new offering. During any calendar year, participants may not purchase shares of common stock having a value greater than $25,000, based on the fair market value per share of the common stock at the beginning of an offering period.

Valuation of Equity Awards

Stock Options

The fair value of each option granted was estimated on the date of grant using the Black-Scholes option-pricing model with the following assumptions:

•

Expected term—The expected term of the option awards represents the period of time between the grant date of the option awards and the date the option awards are either exercised, converted or canceled, including an estimate for those option awards still outstanding. The Company used the simplified method, as permitted by the SEC for companies with a limited history of stock option exercise activity, to determine the expected term for its option grants.


•	Expected volatility—The expected volatility was calculated based on the Company’s historical stock prices, supplemented as necessary with historical volatility of the common stock of several peer companies with characteristics similar to those of the Company.


•	Risk-free interest rate—The risk-free interest rate was based on the U.S. Treasury yield curve in effect at the time of grant and with a maturity that approximated the Company’s expected term.


•	Dividend yield—The dividend yield was based on the Company’s dividend history and the anticipated dividend payout over its expected term.

The following table presents the weighted-average grant date fair value of options granted for the periods presented and the assumptions used to estimate those values using a Black-Scholes option pricing model.



	Years Ended December 31,
	2019			2018			2017
Weighted average grant date fair value	$	9.16		$	2.83		$	0.76
Expected term (in years)	3.8			4.0			4.4
Expected volatility	89.1		%	88.5		%	83.9		%
Annual risk-free rate of return	2.1		%	2.6		%	1.8		%
Dividend yield	—		%	—		%	—		%

Restricted Stock Units

The fair value of the Company’s restricted stock units (“RSU”) awards granted is based upon the closing price of the Company’s stock price on the date of grant.

Performance Stock Units

The fair value of the Company’s non-market performance stock units (“PSU”) awards granted was based upon the closing price of the Company’s stock price on the date of grant. The fair value of awards of the Company’s PSU awards containing market conditions was determined using a Monte Carlo simulation model based upon the terms of the conditions, the expected volatility of the underlying security, and other relevant factors.

Stock-based Compensation Expense

Stock-based compensation expense for all stock-based awards expected to vest is measured at fair value on the date of grant and recognized ratably over the requisite service period. The following table summarizes the components of total stock-based compensation expense included in the consolidated statements of operations for the periods presented.



	Years Ended December 31,
	2019		2018		2017
	(In thousands)
Cost of revenues	$	1,650	$	1,071	$	1,072
Research and development	4,897		2,940		2,573
Sales and marketing	5,678		3,074		1,157
General and administrative	7,216		4,347		1,925
Restructuring	735		—		—
Total	$	20,176	$	11,432	$	6,727

The following table summarizes the various types of stock-based compensation expense for the periods presented.



	Years Ended December 31,
	2019		2018		2017
	(In thousands)
Stock options, RSUs, and PSUs	$	19,216	$	10,691	$	5,559
Employee stock purchase plan	960		741		1,168
Total	$	20,176	$	11,432	$	6,727

As of December 31, 2019, there was approximately $31.5 million of total unrecognized stock-based compensation expense related to unvested equity awards, which are expected to be recognized over a weighted-average period of 2.3 years.

Equity Awards Activity

Stock Options

The following is a summary of stock option activity.



	Number of Shares Outstanding		Weighted- Average Exercise Price per Share		Weighted- Average Remaining Contractual Term	Aggregate Intrinsic Value ⁽¹⁾
	(In thousands)				(Years)	(In thousands)
Outstanding at December 31, 2016	8,730		$	4.55
Granted	4,500		1.22
Exercised	(425	)	0.51			$	544
Canceled	(4,379	)	6.91
Outstanding at December 31, 2017	8,426		$	1.77
Granted	213		4.43
Exercised	(1,346	)	1.75			5,096
Canceled	(521	)	2.94
Outstanding at December 31, 2018	6,772		$	1.76
Granted	43		14.58
Exercised	(2,616	)	1.22			31,093
Canceled	(102	)	4.07
Outstanding at December 31, 2019	4,097		$	2.18	4.3	$	98,103
Vested and expected to vest at December 31, 2019	4,097		$	2.18	4.3	$	98,103
Exercisable at December 31, 2019	2,887		$	2.44	4.1	$	68,397

(1)

The intrinsic value of options exercised is based upon the value of the Company’s stock at exercise. The intrinsic value of options outstanding, vested and expected to vest, and exercisable as of December 31, 2019 is based on the closing price of the Company’s stock fair value on December 31, 2019 or the earlier of the last trading day prior to December 31, 2019, if December 31, 2019 is a non-trading day. The Company’s stock fair value used in this computation was $26.13 per share.

The following table summarizes information about stock options outstanding at December 31, 2019.



	Options Outstanding				Options Exercisable
Range of Exercise Prices	Number of Shares	Weighted- Average Remaining Life	Weighted- Average Exercise Price		Number of Shares	Weighted- Average Exercise Price
	(In thousands)	(Years)			(In thousands)
$0.64 —– $1.11	774	5.0	$	0.82	518	$	0.78
$1.29 —– $1.29	1,000	4.7	1.29		563	1.29
$1.31 —– $1.31	1,309	4.3	1.31		975	1.31
$1.37 —– $7.50	867	3.2	4.18		702	4.57
$7.68 —– $14.58	147	3.4	11.45		129	11.02
Total	4,097	4.3	$	2.18	2,887	$	2.44

Restricted Stock Units

The following is a summary of RSU activity.



	Number of Shares Outstanding		Weighted- Average Fair Value per Share at Grant Date		Weighted- Average Remaining Contractual Term	Aggregate Intrinsic Value ⁽¹⁾
	(In thousands)				(Years)	(In thousands)
Outstanding at December 31, 2016	606		$	9.33
Granted	5,418		1.46
Vested	(885	)	3.81			$	932
Canceled	(1,634	)	1.90
Outstanding at December 31, 2017	3,505		$	2.03
Granted	3,152		4.45
Vested	(1,399	)	2.75			6,657
Canceled	(906	)	2.17
Outstanding at December 31, 2018	4,352		$	3.52
Granted	2,112		11.50
Vested	(1,707	)	3.87			27,156
Canceled	(494	)	4.81
Outstanding at December 31, 2019	4,263		$	7.19	1.3	$	111,387
Expected to vest at December 31, 2019	4,263		$	7.19	1.3	$	111,387

(1)

The intrinsic value of RSUs vested is based upon the value of the Company’s stock when vested. The intrinsic value of RSUs outstanding and expected to vest as of December 31, 2019 is based on the closing price of the Company’s stock on December 31, 2019 or the earlier of the last trading day prior to December 31, 2019, if December 31, 2019 is a non-trading day. The Company’s stock fair value used in this computation was $26.13 per share.

On April 3, 2017, the Company commenced a Tender Offer (the “Offer”) to exchange out of the money stock options for RSUs. The Offer expired on May 1, 2017. Pursuant to the Offer, the Company accepted elections to exchange options to purchase 2,362,470 shares of common stock and issued replacement awards of RSUs for 733,559 shares of common stock. As the transaction approximated a value-for-value exchange, it did not have a material impact on the Company’s stock-based compensation expense.

Performance Stock Units

The following is a summary of PSU activity.



	Number of Shares Outstanding		Weighted- Average Fair Value per Share at Grant Date		Weighted- Average Remaining Contractual Term	Aggregate Intrinsic Value ⁽¹⁾
	(In thousands)				(Years)	(In thousands)
Outstanding at December 31, 2017	—
Granted	1,477		$	4.65
Vested	—
Canceled	(147	)
Outstanding at December 31, 2018	1,330		$	4.66
Granted	1,052		9.48
Vested	(1,063	)	4.62			$	10,818
Canceled	(364	)	5.16
Outstanding at December 31, 2019	955		$	9.83	0.2	$	24,952

(1)

The intrinsic value of PSUs vested is based upon the value of the Company’s stock when vested. The intrinsic value of PSUs outstanding and expected to vest as of December 31, 2019 is based on the closing price of the Company’s stock on December 31, 2019 or the earlier of the last trading day prior to December 31, 2019, if December 31, 2019 is a non-trading day. The Company’s stock fair value used in this computation was $26.13 per share.

Stock-based compensation expense is measured at the grant date based on the fair value of the award. During the first quarter of 2019 the Company issued PSU grants of 1.0 million shares, of which 0.5 million shares include market conditions. Each grantee is granted a target award of PSUs and may earn between 0% and 200% of the target award depending on the Company’s performance against the performance goals. The grant date fair value of PSUs without market conditions is recognized as expense when the performance condition is probable of being achieved, and then on a graded basis over the requisite service period. The grant date fair value of PSUs with market conditions is recognized as expense on a straight-line basis over the requisite service period. The weighted average estimated fair value of the PSUs without market conditions was $8.80 per share, and the weighted average estimated fair value of the PSUs with market conditions, based on the Monte Carlo model, was $10.70 per share.

Employee Stock Purchase Plan

A summary of ESPP activity for the years presented is as follows: (in thousands, except per share data):



	Years Ended December 31,
	2019		2018		2017
Proceeds from common stock issued under ESPP	$	1,692	$	397	$	313
Shares of common stock issued	315		439		478
Weighted-average price per share	$	5.37	$	0.90	$	0.65

INCOME TAXES

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

INCOME TAXES

The domestic and foreign components of income (loss) before income taxes consisted of the following:



	Years Ended December 31,
	2019		2018			2017
	(In thousands)
United States	$	85,520	$	(14,322	)	$	(47,882	)
Foreign	4,594		4,093			2,541
Income (loss) before income taxes	$	90,114	$	(10,229	)	$	(45,341	)

The income taxes (benefit) provision for the years presented is as follows:



	Years Ended December 31,
	2019			2018			2017
	(In thousands)
Current:
Federal	$	—		$	—		$	—
State	327			42			21
Foreign	1,589			1,233			1,224
	1,916			1,275			1,245
Deferred:
Federal	(56,959		)	(35		)	(1,092		)
State	(17,458		)	(21		)	(21		)
Foreign	1,467			179			(281		)
	(72,950		)	123			(1,394		)
Income taxes (benefit) provision	$	(71,034	)	$	1,398		$	(149	)

A reconciliation of the income tax (benefit) provision and the amount computed by applying the statutory federal income tax rate of 21% in 2019 and 2018 and 34% in 2017 to income (loss) before income taxes for the years presented is as follows:



	Years Ended December 31,
	2019			2018			2017
	(In thousands)
Income tax (benefit) provision at statutory federal rate	$	18,929		$	(2,148	)	$	(15,416	)
State taxes, net of federal benefit	(17,197		)	17			(64		)
Change in valuation allowance	(71,300		)	8,198			(20,571		)
Foreign tax rate and tax law differential	1,206			313			(133		)
Tax credits	(1,803		)	(378		)	(382		)
Stock-based compensation	(8,072		)	(953		)	761
Other permanent items	31			235			479
Other nondeductible/nontaxable items	2,765			(5,112		)	930
Uncertain tax positions	504			107			106
Tax law changes	—			—			34,141
GILTI	1,086			917			—
Section 162(m)	2,817			202			—
Income tax (benefit) provision	$	(71,034	)	$	1,398		$	(149	)

A summary of significant components of the Company’s deferred tax assets and liabilities as of December 31, 2019 and 2018 is as follows (in thousands):



	December 31,
	2019			2018
Deferred tax assets:
Allowances and reserves	$	10,726		$	10,022
Net operating loss and tax credit carryforwards	54,369			71,568
Stock-based compensation	3,753			3,662
Deferred revenue	16,736			19,562
Fixed assets and intangibles	2,720			3,836
Sec. 163(j) interest carryforward	—			2,064
Other	1,109			2,084
Subtotal	89,413			112,798
Less valuation allowance	—			(98,631		)
Total deferred tax assets, net of valuation allowance	89,413			14,167
Deferred tax liabilities:
Goodwill	(1,368		)	(1,070		)
Unremitted foreign earnings	(5		)	(16		)
Deferred cost of goods sold	(14,374		)	(12,655		)
Total deferred tax liabilities	(15,747		)	(13,741		)
Net deferred tax asset	$	73,666		$	426

The Company's accounting for deferred taxes involves the evaluation of a number of factors concerning the realizability of the Company's deferred tax assets. Assessing the realizability of deferred tax assets is dependent upon several factors, including the likelihood and amount, if any, of future taxable income in relevant jurisdictions during the periods in which those temporary differences become deductible. The Company's management forecasts taxable income by considering all available positive and negative evidence including its history of operating income or losses and its financial plans and estimates which are used to manage the business. These assumptions require significant judgment about future taxable income. The amount of deferred tax assets considered realizable is subject to adjustment in future periods if estimates of future taxable income are reduced.

In the fourth quarter of fiscal year 2019, the Company's management determined, based on the Company's recent history of earnings coupled with its forecasted profitability, that it is more likely than not that all of deferred tax assets will be realized in the foreseeable future. Accordingly, in the fourth quarter of fiscal year 2019, the Company released $92.9 million of the valuation allowance on its deferred tax assets, related to its federal and state deferred tax assets.

The Company has net operating loss carryforwards for federal and California income tax purposes of approximately $147.4 million and $78.9 million, respectively, as of December 31, 2019. The federal and state net operating loss carryforwards, if not utilized, will expire beginning in 2028.

The Company has approximately $12.4 million of federal research credit and $11.3 million of state research credit carryforwards. The federal credits begin to expire in 2026 and the state credits can be carried forward indefinitely.

Utilization of some of the federal and state net operating loss and credit carryforwards are subject to annual limitations due to the “change in ownership” provisions of the Internal Revenue Code of 1986 and similar state provisions. The Company has completed a Section 382 analysis through December 31, 2019, which indicated no such change has occurred through December 31, 2019.

The accounting for uncertain tax positions prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. The Company is required to recognize in the financial statements the impact of a tax position, if that position is more-likely-than-not of being sustained on audit, based on the technical merits of the position. The Company recorded a net charge for unrecognized tax benefits in 2019 of $0.3 million.

The Company does not have any tax positions for which it is reasonably possible the total amount of gross unrecognized tax benefits will increase or decrease over the next year. The unrecognized tax benefits may increase or change during the next year for items that arise in the ordinary course of business.

A tabular reconciliation of the total amounts of unrecognized tax benefits for the years presented is as follows (in thousands):



	Years Ended December 31,
	2019			2018			2017
Unrecognized tax benefits—at beginning of year	$	6,325		$	6,106		$	6,016
Decreases in balances related to tax positions taken in prior years	(370		)	—			(135		)
Increases in balances related to tax positions taken in current year	771			329			306
Lapses in statutes of limitations	(137		)	(110		)	(81		)
Unrecognized tax benefits—at end of year	$	6,589		$	6,325		$	6,106

The Company includes interest and penalties related to unrecognized tax benefits within the benefit from (provision for) income taxes. As of years ended December 31, 2019 and 2018, the total amount of gross interest and penalties accrued in each year was immaterial. Both the unrecognized tax benefits and the associated interest and penalties that are not expected to result in payment or receipt of cash within one year are classified as other non-current liabilities in the consolidated balance sheets. In connection with tax matters, the Company’s interest and penalty expense recognized in 2019, 2018 and 2017 in the consolidated statements of operations was immaterial.

The Company’s tax returns continue to remain effectively subject to examination by U.S. federal authorities for the years 2006 through 2019 and by California state authorities for the years 2006 through 2019 due to use and carryovers of net operating losses and credits.

CONCENTRATION OF CREDIT RISK AND MAJOR CUSTOMERS	12 Months Ended
CONCENTRATION OF CREDIT RISK AND MAJOR CUSTOMERS	Dec. 31, 2019
Risks and Uncertainties [Abstract]
CONCENTRATION OF CREDIT RISK AND MAJOR CUSTOMERS	CONCENTRATION OF CREDIT RISK AND MAJOR CUSTOMERS The Company is potentially subject to financial instrument concentration of credit risk through its cash and cash equivalents and accounts receivable. The Company places its cash and cash equivalents with high quality institutions and performs periodic evaluations of their relative credit standing. Accounts receivable can be potentially exposed to a concentration of credit risk with its major customers. As of December 31, 2019, amounts due from three customers represented approximately 34%, 14% and 11% of the total accounts receivable balance. As of December 31, 2018, amounts due from two customers represented 22% and 13% of the total accounts receivable balance. In 2019, two customers accounted for approximately 21% and 12% of total net revenues. In 2018, one customer accounted for approximately 19% of total net revenues. In 2017, two customers accounted for approximately 15% and 11% of total net revenues.

NET INCOME (LOSS) PER SHARE

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

NET INCOME (LOSS) PER SHARE

Basic net income (loss) per share is computed by dividing net income (loss) by the weighted average number of shares of common stock outstanding during the period. Diluted net income (loss) per share is computed in a similar manner, but it also includes the effect of potential common shares outstanding during the period, when dilutive. Potential common shares include Stock Options, RSUs, PSUs, shares to be purchased under the Company’s ESPP, the Notes due 2023, the Notes due 2024 and warrants issued in conjunction with the Notes due 2024. The dilutive effect of potentially dilutive common shares is reflected in diluted earnings per share by application of the treasury stock method for stock options, RSUs, PSUs, warrants, Notes due 2024 and shares to be purchased under the ESPP, and by application of the if-converted method for the Notes due 2023. To the extent these potential common shares are antidilutive, they are excluded from the calculation of diluted net income (loss) per share.

The following table presents the computation of basic and diluted net income (loss) per share for the periods presented.



	Years Ended December 31,
	2019		2018			2017
	(In thousands, except per share data)
Numerator:
Net income (loss)	$	161,148	$	(11,627	)	$	(45,192	)
Notes due 2023 interest and financing costs, net	1,088		—			—
Adjusted net income (loss)	$	162,236	$	(11,627	)	$	(45,192	)

Denominator:
Shares used in basic per share amounts:
Weighted average common shares outstanding	116,713		99,619			82,939

Shares used in diluted per share amounts:
Weighted average common shares outstanding	116,713		99,619			82,939
Effect of dilutive securities:
Employee stock-based awards	8,964		—			—
Warrants	—		—			—
Notes due 2024	451		—			—
Notes due 2023	5,516		—			—
Weighted average common shares outstanding for diluted calculation	131,644		99,619			82,939

Basic and diluted net income (loss) per share
Net income (loss) per share, basic	$	1.38	$	(0.12	)	$	(0.54	)
Net income (loss) per share, diluted	$	1.23	$	(0.12	)	$	(0.54	)

The following outstanding shares of common stock equivalents were excluded from the calculation of the diluted net income (loss) per share attributable to common stockholders because their effect would have been antidilutive.



	Years Ended December 31,
	2019	2018	2017
	(In thousands)
Employee stock options	27	7,710	8,433
RSUs and PSUs	158	5,273	3,029
Warrants to purchase common stock	300	—	1,083
Notes due 2023	—	11,701	—
Total	485	24,684	12,545

Diluted earnings per shares for the year ended December 31, 2019 includes the dilutive effect of stock options, RSUs, PSUs, and shares to be purchased under the ESPP, the Notes due 2023 and Notes due 2024. Certain common stock issuable under stock options, RSUs, PSUs and warrants issued in conjunction with the Notes due 2024 have been omitted from the diluted net income per share calculation because including such shares would have been antidilutive.

Since the Company has the intent and ability to settle the aggregate principal amount of the Notes due 2024 in cash and any excess in shares of the Company’s common stock, the Company uses the treasury stock method for calculating any potential dilutive effect of the conversion spread on diluted net income per share, if applicable. In order to compute the dilutive effect, the number of shares included in the denominator of diluted net income per share is determined by dividing the conversion spread value of the “in-the-money” Notes due 2024 by the Company’s average share price during the period and including the resulting share amount in the diluted net income per share denominator. The conversion spread will have a dilutive impact on net income per share of common stock when the average market price of the Company’s common stock for a given period exceeds the conversion price of $20.5010 per share for the Notes due 2024. The Company’s weighted average common stock price since the issuance of the Notes due 2024 was above the conversion price, resulting in an impact on the diluted net income per share.

Diluted earnings per shares for the years ended December 31, 2018 and 2017, excludes potential common stock issuable under stock options, RSUs, PSUs, and shares to be purchased under the ESPP and the Notes due 2023, as the Company incurred a net loss during these periods and including such shares would have been antidilutive.

SEGMENT AND GEOGRAPHIC INFORMATION

12 Months Ended

Dec. 31, 2019

Segment Reporting [Abstract]

SEGMENT AND GEOGRAPHIC INFORMATION

The Company’s chief operating decision maker is the Chief Executive Officer. The Chief Executive Officer reviews financial information presented on a consolidated basis. The Company has one business activity, which entails the design, development, manufacture and sale of solutions for the solar photovoltaic industry. There are no segment managers who are held accountable for operations, operating results or plans for levels or components below the consolidated unit level. Accordingly, management has determined that the Company has a single operating and reportable segment.

The following tables present net revenues (based on the destination of shipments) and long-lived assets by geographic region as of and for the periods presented (in thousands):

Net Revenues



	Years Ended December 31,
	2019		2018		2017
	(In thousands)
United States	$	523,577	$	219,600	$	199,565
International	100,756		96,559		86,601
Total	$	624,333	$	316,159	$	286,166

Long-Lived Assets



	December 31,
	2019		2018
	(In thousands)
United States	$	16,754	$	13,146
China	4,635		5,504
Mexico	3,510		—
Other	4,037		2,348
Total	$	28,936	$	20,998

RELATED PARTY	12 Months Ended
RELATED PARTY	Dec. 31, 2019
Related Party Transactions [Abstract]
RELATED PARTY	RELATED PARTY The Company sells products to SunPower under the August 2018 MSA. As of December 31, 2019 and 2018, SunPower via its wholly owned subsidiary, held 6.5 million shares and 7.5 million shares, respectively, of the Company’s common stock. Revenue recognized under the MSA for the years ended December 31, 2019 and 2018 was $70.9 million and $12.4 million, respectively, net of amortization of the customer relationship intangible asset (see Note 6. “Goodwill and Intangible Assets”). As of December 31, 2019 and 2018, the Company had accounts receivable of $15.9 million and $10.3 million, respectively, from SunPower. As of December 31, 2019, the Company received $5.2 million as a safe harbor prepayment from SunPower in the fourth quarter of 2019 for product delivered in the first quarter of 2020. In 2018, a member of the Company’s board of directors and one of its principal stockholders, Thurman John Rodgers, purchased $5.0 million aggregate principal amount of the Notes due 2023 in a concurrent private placement. As of both December 31, 2019 and December 31, 2018, $5.0 million aggregate principal amount of the Notes due 2023 were outstanding. See Note 11. “Debt” for additional information related to this purchase.

ACQUISITION

12 Months Ended

Dec. 31, 2019

Business Combinations [Abstract]

ACQUISITION

On August 9, 2018, the Company completed its acquisition of SunPower’s microinverter business pursuant to an APA by which the Company acquired certain assets and liabilities of SunPower relating to the research and development and manufacturing of microinverters. The acquisition was accounted for as a business combination and, accordingly, the total purchase price was allocated to the preliminary net tangible and intangible assets and liabilities based on their preliminary fair values on the acquisition date.

In conjunction with the APA, the Company entered into an MSA with SunPower. Pursuant to the terms of the MSA, the Company becomes the exclusive supplier of MLPEs for SunPower’s residential business in the U.S. for a period of five years. The resulting customer relationship intangible is accounted for as a distinct transaction from the acquired business.

The acquisition date fair value of the consideration transferred was approximately $57.3 million, which consisted of the following (in thousands):



Cash consideration	$	25,000
Common stock issued	32,319
Total	$	57,319

The fair value of the Company’s 7.5 million shares of common stock issued, valued at $32.3 million, was determined based on the closing market price of the Company’s common stock on the acquisition date, less a discount of 14% to 30% (depending on the year) for lack of marketability as the shares issued are subject to a restriction that limits their trade or transfer with a lock-up period of six months and restrictions on the number of shares that can be transferred by SunPower in each six-month period following the lock-up period.

The following table summarizes the preliminary estimated fair values of the assets acquired and liabilities assumed at the acquisition date (in thousands):



Intangible assets	$	36,200
Goodwill	21,119
Net assets acquired	$	57,319

The excess of the consideration paid over the fair values assigned to the assets acquired and liabilities assumed represents the goodwill resulting from the acquisition. The $21.1 million of goodwill recognized is attributable primarily to the benefits the Company expects to derive from enhanced scale and efficiency to better serve its markets. Goodwill is expected to be deductible over the next 15 years for income tax purposes.

The fair values assigned to tangible and identifiable intangible assets acquired are based on management’s estimates and assumptions. The fair values of assets acquired are preliminary and may be subject to change within the measurement period as the fair value assessments are finalized.

The following table shows the fair value of the separately identifiable intangible assets at the time of acquisition and the period over which each intangible asset will be amortized:



	Preliminary Fair Value		Useful Life
	(In thousands)		(Years)
Developed technology	$	13,100	6
Customer relationship	23,100		9
Total identifiable intangible assets	$	36,200

The developed technology acquired is embedded in the microinverters that SunPower sells to its customers. The Company already has developed microinverter technology and the Company will supply its microinverters to SunPower through the term of the MSA. The Company does not intend to actively use the developed technology acquired from SunPower but does plan to hold the developed technology to prevent others from using it. Therefore, the Company will account for the developed technology as a defensive intangible asset. The Company expects to realize the benefits of the developed technology over the period of time in which the Company will supply microinverters to SunPower. The Company does expect changes in microinverter technology during the life of the customer relationship with SunPower and expects to benefit from preventing competitors’ access to the technology over a period of six years, therefore, the Company will amortize the value of the developed technology intangible asset over a period of six years.

The MSA was negotiated together with the APA and provides the Company with the exclusive right to supply SunPower with MLPEs for a period of five years, with options for renewals. The exclusivity arrangement extends throughout the term of the MSA, which comprises all of the expected cash flows from the customer relationship intangible asset, and was a condition to, and was an essential part of the acquisition of the microinverter business by the Company. As the fair value ascribed to the customer relationship intangible asset represents payments to a customer, the Company will amortize the value of the customer relationship intangible asset as a reduction to revenue using a pattern of economic benefit method over a useful life of nine years.

The table below shows estimated fair values of the assets acquired funded by cash and issuance of common stock at the acquisition date:



	Cash Purchase Price		Issuance of Common Stock		Total Consideration		% of Total Consideration
	(In thousands)
Developed technology and goodwill	$	15,000	$	19,219	$	34,219	60	%
Customer relationship	10,000		13,100		23,100		40	%
Total consideration	$	25,000	$	32,319	$	57,319	100	%

The Company allocated $10.0 million of the $25.0 million paid of the cash purchase price to cash flows from operating activities and the remaining $15.0 million to cash used in investing activities in the consolidated statements of cash flows for the year ended December 31, 2018. The allocation was based on the valuation of the customer relationship relative to the overall consideration. In addition, the Company disclosed $19.2 million from issuance of common stock and $15.0 million of cash purchase price paid for the developed technology and goodwill as investing activities in the consolidated statements of cash flows for the year ended December 31, 2018.

During 2018, total acquisition-related costs were approximately $0.8 million, which were included in general and administrative expenses.

The Company determined it is impractical to include such pro forma information given the difficulty in obtaining the historical financial information for the SunPower microinverter business as the business was part of SunPower and did not have discrete financial information prior to the acquisition. Inclusion of such information would require the Company to make estimates and assumptions regarding the acquired business historical financial results that the Company believes may ultimately prove inaccurate.

SELECTED UNAUDITED QUARTERLY FINANCIAL INFORMATION

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

SELECTED UNAUDITED QUARTERLY FINANCIAL INFORMATION

The following tables show a summary of the Company’s quarterly financial information for each of the four quarters of 2019 and 2018 (in thousands, except per share data):



	Three Months Ended
	March 31, 2019			June 30, 2019			September 30, 2019			December 31, 2019
Net revenues	$	100,150		$	134,094		$	180,057		$	210,032
Cost of revenues	66,811			88,775			115,351			132,151
Gross profit	33,339			45,319			64,706			77,881
Operating expenses:
Research and development	8,524			9,604			11,085			11,168
Sales and marketing	7,433			9,054			9,551			10,690
General and administrative	9,880			8,583			9,895			10,450
Restructuring charges	368			631			469			1,131
Total operating expenses	26,205			27,872			31,000			33,439
Income from operations	7,134			17,447			33,706			44,442
Other expense, net
Interest Income	211			593			894			815
Interest expense	(3,751		)	(1,351		)	(2,286		)	(2,303		)
Other income (expense)	(481		)	(5,480		)	(943		)	1,467
Total other expense, net	(4,021		)	(6,238		)	(2,335		)	(21		)
Income before income taxes	3,113			11,209			31,371			44,421
Income tax benefit (provision)	(348		)	(591		)	(272		)	72,245
Net income	$	2,765		$	10,618		$	31,099		$	116,666
Net income per share, basic	$	0.03		$	0.09		$	0.25		$	0.95
Net income per share, diluted	$	0.02		$	0.08		$	0.23		$	0.88



	Three Months Ended
	March 31, 2018			June 30, 2018			September 30, 2018			December 31, 2018
Net revenues	$	69,972		$	75,896		$	78,002		$	92,289
Cost of revenues	51,657			53,195			52,738			64,124
Gross profit	18,315			22,701			25,264			28,165
Operating expenses:
Research and development	7,620			9,462			8,165			7,340
Sales and marketing	6,227			6,828			7,375			6,617
General and administrative	6,943			6,969			7,510			7,664
Restructuring charges	—			—			2,588			1,541
Total operating expenses	20,790			23,259			25,638			23,162
Income (loss) from operations	(2,475		)	(558		)	(374		)	5,003
Other expense, net
Interest income	93			154			321			490
Interest expense	(2,385		)	(2,423		)	(2,790		)	(3,095		)
Other expense, net	(126		)	(572		)	(379		)	(1,113		)
Total other expense, net	(2,418		)	(2,841		)	(2,848		)	(3,718		)
Income (loss) before income taxes	(4,893		)	(3,399		)	(3,222		)	1,285
Provision for income taxes	(235		)	(339		)	(248		)	(576		)
Net income (loss)	$	(5,128	)	$	(3,738	)	$	(3,470	)	$	709
Net income (loss) per share, basic	$	(0.06	)	$	(0.04	)	$	(0.03	)	$	0.01
Net income (loss) per diluted share	$	(0.06	)	$	(0.04	)	$	(0.03	)	$	0.01

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Basis of Presentation and Consolidation

The accompanying consolidated financial statements are presented in accordance with accounting principles generally accepted in the United States (“U.S.”), or GAAP. The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of income and expenses during the reporting period. Significant estimates and assumptions reflected in the financial statements include revenue recognition, inventory valuation, accrued warranty obligations, incremental borrowing rate for right-of-use assets and lease liability, and tax valuation allowance. These estimates are based on information available as of the date of the financial statements; therefore, actual results could differ materially from management’s estimates using different assumptions or under different conditions.

Revenue Recognition and Cost of Revenues

Contract Liabilities

Revenue Recognition

•

The Company records certain contra revenue promotions as variable consideration and recognizes these promotions at the time the related revenue is recorded.

See Note 3. “Revenue Recognition,” for additional information related to revenue recognition.

Cost of Revenues


•	Products Delivered at a Point in Time. Cost of revenue from these products is recognized when the Company transfers control of the product to the customer, which is generally upon shipment.

•

Products Delivered Over Time. Cost of revenue from these products is recognized over the related service period.

Cash and Cash Equivalents and Restricted Cash

Cash and Cash Equivalents

Restricted Cash

Fair Value of Financial Instruments

Accounts Receivables and Contract Assets

Allowances for Doubtful Accounts

Allowance for Doubtful Accounts

Inventory

Property and Equipment

Capitalized Software Costs

Impairment of Long-Lived Assets

Business Combinations

Goodwill and Intangible Assets

Goodwill

Intangible Assets

Warranty Obligations

Microinverters Sold Through December 31, 2013

Fair Value Option for Microinverters Sold Since January 1, 2014

Warranty for Other Products

Research and Development Costs

Stock-Based Compensation

Leases

The Company combines the lease and non-lease components in determining the operating lease assets and liabilities.

Foreign Currency Translation

Comprehensive Income (Loss)

Income Taxes

Recently Adopted Accounting Pronouncements and Recently Issued Accounting Pronouncements Not Yet Effective

Recently Adopted Accounting Pronouncements

Recently Issued Accounting Pronouncements Not Yet Effective

Fair Value Measurement


•	Level 1—Valuations based on quoted prices in active markets for identical assets or liabilities that the Company is able to access. Since valuations are based on quoted prices that are readily and regularly available in an active market, valuation of such assets or liabilities do not entail a significant degree of judgment.


•	Level 2—Valuations based on one or more quoted prices in markets that are not active or for which all significant inputs are observable, either directly or indirectly.

•

Level 3—Valuations based on inputs that are unobservable and significant to the overall fair value measurement.

Earnings Per Share

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Schedule of Activity in Allowance for Doubtful Accounts

The following table sets forth activities in the allowance for doubtful accounts for the periods indicated.



	December 31,
	2019			2018			2017
	(In thousands)
Balance, at beginning of year	$	2,138		$	2,378		$	2,921
Net charges to expenses	217			711			476
Write-offs, net of recoveries	(1,791		)	(951		)	(1,019		)
Balance, at end of year	$	564		$	2,138		$	2,378

REVENUE RECOGNITION (Tables)

12 Months Ended

Dec. 31, 2019

Revenue from Contract with Customer [Abstract]

Summary of Revenue Disaggregation

Disaggregated revenue by primary geographical market and timing of revenue recognition for the Company’s single product line are as follows:



	Years Ended December 31,
	2019		2018
	(In thousands)
Primary geographical markets:
United States	$	523,577	$	219,600
International	100,756		96,559
Total	$	624,333	$	316,159

Timing of revenue recognition:
Products delivered at a point in time	$	584,556	$	270,778
Products and services delivered over time	39,777		45,381
Total	$	624,333	$	316,159

Summary of Contract Assets and Contract Liabilities, and Changes in Balances from Contracts with Customers

Significant changes in the balances of contract assets (prepaid expenses and other assets) during the period are as follows (in thousands):



Contract Assets
Balance on December 31, 2018	$	47,664
Amount recognized	(15,144		)
Increase	24,622
Balance as of December 31, 2019	$	57,142

Receivables, and contract assets and contract liabilities from contracts with customers are as follows:



	December 31, 2019		December 31, 2018
	(In thousands)
Receivables	$	145,413	$	78,938
Short-term contract assets (Prepaid expenses and other assets)	15,055		13,516
Long-term contract assets (Other assets)	42,087		34,148
Short-term contract liabilities (Deferred revenues)	81,783		33,119
Long-term contract liabilities (Deferred revenues)	100,204		76,911

Significant changes in the balances of contract liabilities (deferred revenues) during the period are as follows (in thousands):



Contract Liabilities
Balance on December 31, 2018	$	110,030
Revenue recognized	(39,777		)
Increase due to billings	61,825
Increase due to safe harbor prepayments	49,909
Balance as of December 31, 2019	$	181,987

Summary of Estimated Revenue Expected to be Recognized in Future Periods

Estimated revenue expected to be recognized in future periods related to performance obligations that are unsatisfied or partially unsatisfied at the end of the reporting period are as follows:



	December 31, 2019
	(In thousands)
Fiscal year:
2020	$	81,783
2021	30,665
2022	25,633
2023	19,841
2024	14,650
Thereafter	9,415
Total	$	181,987

INVENTORY (Tables)

12 Months Ended

Dec. 31, 2019

Inventory Disclosure [Abstract]

Summary of Inventory

Inventory consist of the following:



	December 31, 2019		December 31, 2018
	(In thousands)
Raw materials	$	4,197	$	970
Finished goods	27,859		15,297
Total inventory	$	32,056	$	16,267

PROPERTY AND EQUIPMENT, NET (Tables)

12 Months Ended

Dec. 31, 2019

Property, Plant and Equipment [Abstract]

Summary of Property and Equipment

Property and equipment consist of the following:



	Estimated Useful Life	December 31,
	Estimated Useful Life	2019			2018
	(Years)	(In thousands)
Equipment and machinery	3-10	$	48,114		$	43,566
Furniture and fixtures	5-10	2,404			2,239
Computer equipment	3-5	1,698			2,958
Capitalized software costs	3-5	11,656			12,114
Leasehold improvements	3-10	8,713			8,482
Construction in process		8,446			3,536
Total		81,031			72,895
Less accumulated depreciation and amortization		(52,095		)	(51,897		)
Property and equipment, net		$	28,936		$	20,998

GOODWILL AND INTANGIBLE ASSETS (Tables)

12 Months Ended

Dec. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Goodwill and Intangible Assets

The Company’s goodwill and purchased intangible assets as of December 31, 2019 and December 31, 2018 are as follows:



	December 31, 2019							December 31, 2018
	Gross		Accumulated Amortization			Net		Gross		Accumulated Amortization			Net
	(In thousands)
Goodwill	$	24,783	$	—		$	24,783	$	24,783	$	—		$	24,783

Intangible assets:
Other indefinite-lived intangibles	$	286	$	—		$	286	$	286	$	—		$	286
Intangible assets with finite lives:
Patents and licensed technology	—		—			—		1,665		(1,665		)	—
Developed technology	13,100		(3,093		)	10,007		13,100		(909		)	12,191
Customer relationships	23,100		(2,814		)	20,286		23,100		(271		)	22,829
Total purchased intangible assets	$	36,486	$	(5,907	)	$	30,579	$	38,151	$	(2,845	)	$	35,306

Schedule of Amortization Expense

Amortization expense related to finite-lived intangible assets are as follows:



	Years Ended December 31,
	2019		2018
	(In thousands)
Developed technology, and patents and licensed technology	$	2,184	$	1,409
Customer relationships	2,543		271
Total amortization expense	$	4,727	$	1,680

ACCRUED LIABILITIES (Tables)

12 Months Ended

Dec. 31, 2019

Payables and Accruals [Abstract]

Schedule of Accrued Liabilities

Accrued liabilities consist of the following:



	December 31, 2019		December 31, 2018
	(In thousands)
Salaries, commissions, incentive compensation and benefits	$	5,524	$	4,107
Customer rebates and sales incentives	24,198		8,527
Freight	4,908		7,286
Operating lease liabilities, current	3,170		—
Other	9,292		9,090
Total accrued liabilities	$	47,092	$	29,010

WARRANTY OBLIGATIONS (Tables)

12 Months Ended

Dec. 31, 2019

Product Warranties Disclosures [Abstract]

Summary of Warranty Activities

The Company’s warranty activities were as follows:



	Years Ended December 31,
	2019			2018			2017
	(In thousands)
Warranty obligations, beginning of period	$	31,294		$	29,816		$	31,414
Accruals for warranties issued during period	5,244			3,040			3,797
Changes in estimates	8,591			6,515			(732		)
Settlements	(10,881		)	(8,579		)	(7,037		)
Increase due to accretion expense	2,326			1,989			2,053
Other	524			(1,487		)	321
Warranty obligations, end of period	37,098			31,294			29,816
Less: current portion	(10,078		)	(8,083		)	(7,427		)
Noncurrent	$	27,020		$	23,211		$	22,389

FAIR VALUE MEASUREMENTS (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis

The following table presents the Company’s liabilities that were measured at fair value on a recurring basis and its categorization within the fair value hierarchy.



	Fair Value Hierarchy	December 31, 2019		December 31, 2018
		(In thousands)
Warranty obligations
Current		$	6,794	$	4,288
Non-current		13,012		7,469
Total warranty obligations measured at fair value	Level 3	$	19,806	$	11,757

Schedule of Changes in Nonfinancial Liabilities Related to Warrant Obligations Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs



	Years Ended December 31,
	2019			2018			2017
	(In thousands)
Balance at beginning of period	$	11,757		$	9,791		$	10,332
Accruals for warranties issued during period	5,244			3,040			3,591
Changes in estimates	6,167			2,455			(4,551		)
Settlements	(6,212		)	(4,030		)	(1,956		)
Increase due to accretion expense	2,326			1,989			2,053
Other	524			(1,488		)	322
Balance at end of period	$	19,806		$	11,757		$	9,791

Summary of Significant Unobservable Inputs used in the Fair Value Measurement of Liabilities Designated as Level 3

As of December 31, 2019 and December 31, 2018, the significant unobservable inputs used in the fair value measurement of the Company’s liabilities designated as Level 3 are as follows:



			Percent Used (Weighted Average)
Item Measured at Fair Value	Valuation Technique	Description of Significant Unobservable Input	December 31, 2019	December 31, 2018
Warranty obligations for microinverters sold since January 1, 2014	Discounted cash flows	Profit element and risk premium	14%	16%
	Discounted cash flows	Credit-adjusted risk-free rate	16%	19%

RESTRUCTURING (Tables)

12 Months Ended

Dec. 31, 2019

Restructuring and Related Activities [Abstract]

Restructuring and Related Costs

Restructuring expense consist of the following:



	Years Ended December 31,
	2019			2018		2017
	(In thousands)
Redundancy and employee severance and benefit arrangements	$	1,575		$	2,228	$	2,827
Asset impairments	1,124			1,601		522
Consultants engaged in restructuring activities	—			—		12,100
Lease loss reserves	(100		)	300		1,468
Total restructuring charges	$	2,599		$	4,129	$	16,917

The following table presents the details of the Company’s restructuring charges under the 2018 Plan for the period indicated:



	Years Ended December 31,
	2019			2018
	(In thousands)
Redundancy and employee severance and benefit arrangements	$	1,575		$	2,228
Asset impairments	1,124			1,636
Lease loss reserves	(100		)	340
Total restructuring charges	$	2,599		$	4,204

Schedule of Restructuring Reserve by Type of Cost

The following table provides information regarding changes in the Company’s 2018 Plan accrued restructuring balance for the periods indicated.



	Redundancy and Employee Severance and Benefits			Lease Loss Reserves and Contractual Obligations			Total
	(In thousands)
Balance as of December 31, 2018	$	904		$	288		$	1,192
Charges	2,699			—			2,699
Cash payments	(1,610		)	—			(1,610		)
Non-cash settlement and other	(1,993		)	(288		)	(2,281		)
Balance as of December 31, 2019	$	—		$	—		$	—

The following table provides information regarding changes in the Company’s 2016 Plan accrued restructuring balance for the periods indicated.



	Employee Severance and Benefits			Lease Loss Reserves and Contractual Obligations			Total
	(In thousands)
Balance as of December 31, 2017	229			1,094			1,323
Charges and adjustments	—			(40		)	(40		)
Cash payments and receipts, net	(229		)	537			308
Balance as of December 31, 2018	—			$	1,591		1,591
Other ⁽¹⁾	—			(1,591		)	(1,591		)
Balance as of December 31, 2019	$	—		$	—		$	—

(1)

Adoption of ASU 2016-02.

DEBT (Tables)

12 Months Ended

Dec. 31, 2019

Debt Disclosure [Abstract]

Schedule of Debt

The following table provides information regarding the Company’s long-term debt.



	December 31, 2019			December 31, 2018
	(In thousands)
Convertible notes
Notes due 2024	$	132,000		$	—
Less: unamortized discount and issuance costs	(35,815		)	—
Carrying amount of Notes due 2024	96,185			—

Notes due 2023	5,000			65,000
Less: unamortized issuance costs	(143		)	(2,361		)
Carrying amount of Notes due 2023	4,857			62,639

Term loan	—			41,524
Less: unamortized discount and issuance costs	—			(1,059		)
Carrying amount of term loan	—			40,465

Sale of long-term financing receivable recorded as debt	4,501			6,679
Total carrying amount of debt	105,543			109,783
Less: current portion term loan	—			(25,417		)
Less: current portion of long-term financing receivable recorded as debt	(2,884		)	(2,738		)
Long-term debt	$	102,659		$	81,628

The following table presents the total amount of interest cost recognized relating to the Notes due 2024:



	Year Ended December 31, 2019
	(In thousands)
Contractual interest expense	$	759
Amortization of debt discount	3,492
Amortization of debt issuance costs	375
Total interest cost recognized	$	4,626

The following table presents the amount of interest cost recognized relating to the contractual interest coupon and the amortization of debt issuance costs of the Notes due 2023.



	Years Ended December 31,
	2019		2018
	(In thousands)
Contractual interest expense	$	1,226	$	975
Amortization of debt issuance costs	245		193
Total interest costs recognized	$	1,471	$	1,168

COMMITMENTS AND CONTINGENT LIABILITIES (Tables)

12 Months Ended

Dec. 31, 2019

Commitments and Contingencies Disclosure [Abstract]

Components of Lease

The components of lease expense are presented as follows:



	Year Ended December 31, 2019
	(In thousands)
Operating lease costs	$	4,041

The components of lease liabilities are presented as follows:



	December 31, 2019
	(In thousands)
Operating lease liabilities, current (Accrued liabilities)	$	3,170
Operating lease liabilities, noncurrent (Other liabilities)	9,542
Total operating lease liabilities	$	12,712

Supplemental lease information:
Weighted average remaining lease term	5.5 years
Weighted average discount rate	8.6%

Supplemental cash flow and other information related to operating leases, are as follows:



	Year Ended December 31, 2019
	(In thousands)
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	3,636

Non-cash investing activities:
Lease liabilities arising from obtaining right-of-use assets	$	4,834

Schedule of Future Minimum Rental Payments for Operating Leases

Undiscounted cash flows of operating lease liabilities as of December 31, 2019 are as follows:



	Lease Amounts
	(In thousands)
Year:
2020	$	4,156
2021	4,238
2022	2,927
2023	2,188
2024	921
2025 and thereafter	740
Total lease payments	15,170
Less: imputed lease interest	(2,458		)
Total lease liabilities	$	12,712

Schedule of Future Minimum Rental Payments for Operating Leases (Prior Year)



	Lease Amounts
	(In thousands)
Year:
2019	$	3,738
2020	3,532
2021	3,276
2022	1,810
2023	945
Thereafter	1,252
Total	14,553
Sublease income to be recognized in the future under noncancelable subleases	(922		)
Net operating lease minimum payments	$	13,631

STOCK-BASED COMPENSATION (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Summary of the Components of Total Stock-Based Compensation Expense

The following table summarizes the components of total stock-based compensation expense included in the consolidated statements of operations for the periods presented.



	Years Ended December 31,
	2019		2018		2017
	(In thousands)
Cost of revenues	$	1,650	$	1,071	$	1,072
Research and development	4,897		2,940		2,573
Sales and marketing	5,678		3,074		1,157
General and administrative	7,216		4,347		1,925
Restructuring	735		—		—
Total	$	20,176	$	11,432	$	6,727

Summary of Stock-Based Compensation Associated with Each Type of Award

The following table summarizes the various types of stock-based compensation expense for the periods presented.



	Years Ended December 31,
	2019		2018		2017
	(In thousands)
Stock options, RSUs, and PSUs	$	19,216	$	10,691	$	5,559
Employee stock purchase plan	960		741		1,168
Total	$	20,176	$	11,432	$	6,727

Summary of the Weighted-Average Grant Date Fair Value of Options Granted



	Years Ended December 31,
	2019			2018			2017
Weighted average grant date fair value	$	9.16		$	2.83		$	0.76
Expected term (in years)	3.8			4.0			4.4
Expected volatility	89.1		%	88.5		%	83.9		%
Annual risk-free rate of return	2.1		%	2.6		%	1.8		%
Dividend yield	—		%	—		%	—		%

Summary of Stock Option Activity

The following is a summary of stock option activity.



	Number of Shares Outstanding		Weighted- Average Exercise Price per Share		Weighted- Average Remaining Contractual Term	Aggregate Intrinsic Value ⁽¹⁾
	(In thousands)				(Years)	(In thousands)
Outstanding at December 31, 2016	8,730		$	4.55
Granted	4,500		1.22
Exercised	(425	)	0.51			$	544
Canceled	(4,379	)	6.91
Outstanding at December 31, 2017	8,426		$	1.77
Granted	213		4.43
Exercised	(1,346	)	1.75			5,096
Canceled	(521	)	2.94
Outstanding at December 31, 2018	6,772		$	1.76
Granted	43		14.58
Exercised	(2,616	)	1.22			31,093
Canceled	(102	)	4.07
Outstanding at December 31, 2019	4,097		$	2.18	4.3	$	98,103
Vested and expected to vest at December 31, 2019	4,097		$	2.18	4.3	$	98,103
Exercisable at December 31, 2019	2,887		$	2.44	4.1	$	68,397

(1)

Summary of Stock Option Outstanding

The following table summarizes information about stock options outstanding at December 31, 2019.



	Options Outstanding				Options Exercisable
Range of Exercise Prices	Number of Shares	Weighted- Average Remaining Life	Weighted- Average Exercise Price		Number of Shares	Weighted- Average Exercise Price
	(In thousands)	(Years)			(In thousands)
$0.64 —– $1.11	774	5.0	$	0.82	518	$	0.78
$1.29 —– $1.29	1,000	4.7	1.29		563	1.29
$1.31 —– $1.31	1,309	4.3	1.31		975	1.31
$1.37 —– $7.50	867	3.2	4.18		702	4.57
$7.68 —– $14.58	147	3.4	11.45		129	11.02
Total	4,097	4.3	$	2.18	2,887	$	2.44

Summary of Restricted Stock Unit Activity

The following is a summary of RSU activity.



	Number of Shares Outstanding		Weighted- Average Fair Value per Share at Grant Date		Weighted- Average Remaining Contractual Term	Aggregate Intrinsic Value ⁽¹⁾
	(In thousands)				(Years)	(In thousands)
Outstanding at December 31, 2016	606		$	9.33
Granted	5,418		1.46
Vested	(885	)	3.81			$	932
Canceled	(1,634	)	1.90
Outstanding at December 31, 2017	3,505		$	2.03
Granted	3,152		4.45
Vested	(1,399	)	2.75			6,657
Canceled	(906	)	2.17
Outstanding at December 31, 2018	4,352		$	3.52
Granted	2,112		11.50
Vested	(1,707	)	3.87			27,156
Canceled	(494	)	4.81
Outstanding at December 31, 2019	4,263		$	7.19	1.3	$	111,387
Expected to vest at December 31, 2019	4,263		$	7.19	1.3	$	111,387

(1)

Share-based Compensation, Performance Shares Award Outstanding Activity

The following is a summary of PSU activity.



	Number of Shares Outstanding		Weighted- Average Fair Value per Share at Grant Date		Weighted- Average Remaining Contractual Term	Aggregate Intrinsic Value ⁽¹⁾
	(In thousands)				(Years)	(In thousands)
Outstanding at December 31, 2017	—
Granted	1,477		$	4.65
Vested	—
Canceled	(147	)
Outstanding at December 31, 2018	1,330		$	4.66
Granted	1,052		9.48
Vested	(1,063	)	4.62			$	10,818
Canceled	(364	)	5.16
Outstanding at December 31, 2019	955		$	9.83	0.2	$	24,952

(1)

Schedule of Share-based Compensation, Employee Stock Purchase Plan, Activity

A summary of ESPP activity for the years presented is as follows: (in thousands, except per share data):



	Years Ended December 31,
	2019		2018		2017
Proceeds from common stock issued under ESPP	$	1,692	$	397	$	313
Shares of common stock issued	315		439		478
Weighted-average price per share	$	5.37	$	0.90	$	0.65

INCOME TAXES (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Schedule of Domestic and Foreign Components of Loss before Provision for Income Taxes

The domestic and foreign components of income (loss) before income taxes consisted of the following:



	Years Ended December 31,
	2019		2018			2017
	(In thousands)
United States	$	85,520	$	(14,322	)	$	(47,882	)
Foreign	4,594		4,093			2,541
Income (loss) before income taxes	$	90,114	$	(10,229	)	$	(45,341	)

Schedule of Provision for Income Taxes

The income taxes (benefit) provision for the years presented is as follows:



	Years Ended December 31,
	2019			2018			2017
	(In thousands)
Current:
Federal	$	—		$	—		$	—
State	327			42			21
Foreign	1,589			1,233			1,224
	1,916			1,275			1,245
Deferred:
Federal	(56,959		)	(35		)	(1,092		)
State	(17,458		)	(21		)	(21		)
Foreign	1,467			179			(281		)
	(72,950		)	123			(1,394		)
Income taxes (benefit) provision	$	(71,034	)	$	1,398		$	(149	)

Schedule of Effective Income Tax Rate Reconciliation



	Years Ended December 31,
	2019			2018			2017
	(In thousands)
Income tax (benefit) provision at statutory federal rate	$	18,929		$	(2,148	)	$	(15,416	)
State taxes, net of federal benefit	(17,197		)	17			(64		)
Change in valuation allowance	(71,300		)	8,198			(20,571		)
Foreign tax rate and tax law differential	1,206			313			(133		)
Tax credits	(1,803		)	(378		)	(382		)
Stock-based compensation	(8,072		)	(953		)	761
Other permanent items	31			235			479
Other nondeductible/nontaxable items	2,765			(5,112		)	930
Uncertain tax positions	504			107			106
Tax law changes	—			—			34,141
GILTI	1,086			917			—
Section 162(m)	2,817			202			—
Income tax (benefit) provision	$	(71,034	)	$	1,398		$	(149	)

Schedule of Deferred Tax Assets and Liabilities

A summary of significant components of the Company’s deferred tax assets and liabilities as of December 31, 2019 and 2018 is as follows (in thousands):



	December 31,
	2019			2018
Deferred tax assets:
Allowances and reserves	$	10,726		$	10,022
Net operating loss and tax credit carryforwards	54,369			71,568
Stock-based compensation	3,753			3,662
Deferred revenue	16,736			19,562
Fixed assets and intangibles	2,720			3,836
Sec. 163(j) interest carryforward	—			2,064
Other	1,109			2,084
Subtotal	89,413			112,798
Less valuation allowance	—			(98,631		)
Total deferred tax assets, net of valuation allowance	89,413			14,167
Deferred tax liabilities:
Goodwill	(1,368		)	(1,070		)
Unremitted foreign earnings	(5		)	(16		)
Deferred cost of goods sold	(14,374		)	(12,655		)
Total deferred tax liabilities	(15,747		)	(13,741		)
Net deferred tax asset	$	73,666		$	426

Schedule of Reconciliation of Total Amounts of Unrecognized Tax Benefits

A tabular reconciliation of the total amounts of unrecognized tax benefits for the years presented is as follows (in thousands):



	Years Ended December 31,
	2019			2018			2017
Unrecognized tax benefits—at beginning of year	$	6,325		$	6,106		$	6,016
Decreases in balances related to tax positions taken in prior years	(370		)	—			(135		)
Increases in balances related to tax positions taken in current year	771			329			306
Lapses in statutes of limitations	(137		)	(110		)	(81		)
Unrecognized tax benefits—at end of year	$	6,589		$	6,325		$	6,106

NET INCOME (LOSS) PER SHARE (Tables)

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

Schedule of Computation of Basic and Diluted Net Loss Per Share

The following table presents the computation of basic and diluted net income (loss) per share for the periods presented.



	Years Ended December 31,
	2019		2018			2017
	(In thousands, except per share data)
Numerator:
Net income (loss)	$	161,148	$	(11,627	)	$	(45,192	)
Notes due 2023 interest and financing costs, net	1,088		—			—
Adjusted net income (loss)	$	162,236	$	(11,627	)	$	(45,192	)

Denominator:
Shares used in basic per share amounts:
Weighted average common shares outstanding	116,713		99,619			82,939

Shares used in diluted per share amounts:
Weighted average common shares outstanding	116,713		99,619			82,939
Effect of dilutive securities:
Employee stock-based awards	8,964		—			—
Warrants	—		—			—
Notes due 2024	451		—			—
Notes due 2023	5,516		—			—
Weighted average common shares outstanding for diluted calculation	131,644		99,619			82,939

Basic and diluted net income (loss) per share
Net income (loss) per share, basic	$	1.38	$	(0.12	)	$	(0.54	)
Net income (loss) per share, diluted	$	1.23	$	(0.12	)	$	(0.54	)

Schedule of Potentially Dilutive Securities Excluded from the Computation of Diluted Net Loss Per Share



	Years Ended December 31,
	2019	2018	2017
	(In thousands)
Employee stock options	27	7,710	8,433
RSUs and PSUs	158	5,273	3,029
Warrants to purchase common stock	300	—	1,083
Notes due 2023	—	11,701	—
Total	485	24,684	12,545

SEGMENT AND GEOGRAPHIC INFORMATION (Tables)

12 Months Ended

Dec. 31, 2019

Segment Reporting [Abstract]

Summary of Net Revenues and Long-Lived Assets by Geographic Region

The following tables present net revenues (based on the destination of shipments) and long-lived assets by geographic region as of and for the periods presented (in thousands):

Net Revenues



	Years Ended December 31,
	2019		2018		2017
	(In thousands)
United States	$	523,577	$	219,600	$	199,565
International	100,756		96,559		86,601
Total	$	624,333	$	316,159	$	286,166

Long-Lived Assets



	December 31,
	2019		2018
	(In thousands)
United States	$	16,754	$	13,146
China	4,635		5,504
Mexico	3,510		—
Other	4,037		2,348
Total	$	28,936	$	20,998

ACQUISITION (Tables)

12 Months Ended

Dec. 31, 2019

Business Combinations [Abstract]

Summary of consideration transfered for business acquisition

The acquisition date fair value of the consideration transferred was approximately $57.3 million, which consisted of the following (in thousands):



Cash consideration	$	25,000
Common stock issued	32,319
Total	$	57,319

The table below shows estimated fair values of the assets acquired funded by cash and issuance of common stock at the acquisition date:



	Cash Purchase Price		Issuance of Common Stock		Total Consideration		% of Total Consideration
	(In thousands)
Developed technology and goodwill	$	15,000	$	19,219	$	34,219	60	%
Customer relationship	10,000		13,100		23,100		40	%
Total consideration	$	25,000	$	32,319	$	57,319	100	%

Summary of fair values of assets acquired and liabilities assumed

The following table summarizes the preliminary estimated fair values of the assets acquired and liabilities assumed at the acquisition date (in thousands):



Intangible assets	$	36,200
Goodwill	21,119
Net assets acquired	$	57,319

Summary of identifiable intangible assets acquired

The following table shows the fair value of the separately identifiable intangible assets at the time of acquisition and the period over which each intangible asset will be amortized:



	Preliminary Fair Value		Useful Life
	(In thousands)		(Years)
Developed technology	$	13,100	6
Customer relationship	23,100		9
Total identifiable intangible assets	$	36,200

SELECTED UNAUDITED QUARTERLY FINANCIAL INFORMATION (Tables)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information

The following tables show a summary of the Company’s quarterly financial information for each of the four quarters of 2019 and 2018 (in thousands, except per share data):



	Three Months Ended
	March 31, 2019			June 30, 2019			September 30, 2019			December 31, 2019
Net revenues	$	100,150		$	134,094		$	180,057		$	210,032
Cost of revenues	66,811			88,775			115,351			132,151
Gross profit	33,339			45,319			64,706			77,881
Operating expenses:
Research and development	8,524			9,604			11,085			11,168
Sales and marketing	7,433			9,054			9,551			10,690
General and administrative	9,880			8,583			9,895			10,450
Restructuring charges	368			631			469			1,131
Total operating expenses	26,205			27,872			31,000			33,439
Income from operations	7,134			17,447			33,706			44,442
Other expense, net
Interest Income	211			593			894			815
Interest expense	(3,751		)	(1,351		)	(2,286		)	(2,303		)
Other income (expense)	(481		)	(5,480		)	(943		)	1,467
Total other expense, net	(4,021		)	(6,238		)	(2,335		)	(21		)
Income before income taxes	3,113			11,209			31,371			44,421
Income tax benefit (provision)	(348		)	(591		)	(272		)	72,245
Net income	$	2,765		$	10,618		$	31,099		$	116,666
Net income per share, basic	$	0.03		$	0.09		$	0.25		$	0.95
Net income per share, diluted	$	0.02		$	0.08		$	0.23		$	0.88



	Three Months Ended
	March 31, 2018			June 30, 2018			September 30, 2018			December 31, 2018
Net revenues	$	69,972		$	75,896		$	78,002		$	92,289
Cost of revenues	51,657			53,195			52,738			64,124
Gross profit	18,315			22,701			25,264			28,165
Operating expenses:
Research and development	7,620			9,462			8,165			7,340
Sales and marketing	6,227			6,828			7,375			6,617
General and administrative	6,943			6,969			7,510			7,664
Restructuring charges	—			—			2,588			1,541
Total operating expenses	20,790			23,259			25,638			23,162
Income (loss) from operations	(2,475		)	(558		)	(374		)	5,003
Other expense, net
Interest income	93			154			321			490
Interest expense	(2,385		)	(2,423		)	(2,790		)	(3,095		)
Other expense, net	(126		)	(572		)	(379		)	(1,113		)
Total other expense, net	(2,418		)	(2,841		)	(2,848		)	(3,718		)
Income (loss) before income taxes	(4,893		)	(3,399		)	(3,222		)	1,285
Provision for income taxes	(235		)	(339		)	(248		)	(576		)
Net income (loss)	$	(5,128	)	$	(3,738	)	$	(3,470	)	$	709
Net income (loss) per share, basic	$	(0.06	)	$	(0.04	)	$	(0.03	)	$	0.01
Net income (loss) per diluted share	$	(0.06	)	$	(0.04	)	$	(0.03	)	$	0.01

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
Fair Value, Option, Quantitative Disclosures [Line Items]
Restricted cash	$ 44,700,000	$ 0	$ 0
Asset impairment	1,100,000	1,600,000	800,000
Goodwill, impairment loss	0	0	0
Impairment of intangible assets	0	0	$ 0
Operating lease, right of use asset	10,117,000
Other liabilities	11,817,000	3,250,000
Accrued liabilities	47,092,000	29,010,000
Other assets	$ 44,620,000	$ 36,548,000
Monitoring Hardware And Service
Fair Value, Option, Quantitative Disclosures [Line Items]
Capitalized contract cost, amortization period	6 years
First and Second Generation
Fair Value, Option, Quantitative Disclosures [Line Items]
Product warranty, term	15 years
Third and Fourth Generation
Fair Value, Option, Quantitative Disclosures [Line Items]
Product warranty, term	25 years
Envoy Communications Gateway
Fair Value, Option, Quantitative Disclosures [Line Items]
Product warranty, term	5 years
AC Battery Storage Solution
Fair Value, Option, Quantitative Disclosures [Line Items]
Product warranty, term	10 years
Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Property, plant and equipment, useful life	3 years
Intangible assets, estimated useful life	3 years
Period failure rate measurement lags product sale	3 months
Minimum \| Communication Accessories
Fair Value, Option, Quantitative Disclosures [Line Items]
Service period	5 years
Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Property, plant and equipment, useful life	10 years
Intangible assets, estimated useful life	9 years
Product warranty, term	25 years
Period failure rate measurement lags product sale	9 months
Maximum \| Communication Accessories
Fair Value, Option, Quantitative Disclosures [Line Items]
Service period	12 years
Accounting Standards Update 2016-02
Fair Value, Option, Quantitative Disclosures [Line Items]
Operating lease, right of use asset				$ 8,400,000
Other liabilities				6,800,000
Accrued liabilities				1,500,000
Other assets				$ (100,000)

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Schedule of Activity in Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance, at beginning of year	$ 2,138	$ 2,378	$ 2,921
Net charges to expenses	217	711	476
Write-offs, net of recoveries	(1,791)	(951)	(1,019)
Balance, at end of year	$ 564	$ 2,138	$ 2,378

REVENUE RECOGNITION - Summary of Disaggregated Revenue by Primary Geographical Market and Timing of Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues	$ 210,032	$ 180,057	$ 134,094	$ 100,150	$ 92,289	$ 78,002	$ 75,896	$ 69,972	$ 624,333	$ 316,159	$ 286,166
Products delivered at a point in time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues									584,556	270,778
Products and services delivered over time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues									39,777	45,381
United States
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues									523,577	219,600	199,565
International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues									$ 100,756	$ 96,559	$ 86,601

REVENUE RECOGNITION - Summary of Contract Assets and Contract Liabilities from Contracts with Customers (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Receivables	$ 145,413	$ 78,938
Short-term contract assets (Prepaid expenses and other assets)	15,055	13,516
Long-term contract assets (Other assets)	42,087	34,148
Short-term contract liabilities (Deferred revenues)	81,783	33,119
Long-term contract liabilities (Deferred revenues)	$ 100,204	$ 76,911

REVENUE RECOGNITION - Narrative (Details)	12 Months Ended
REVENUE RECOGNITION - Narrative (Details)	Dec. 31, 2019 USD ($)
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Contract asset impairment charges	$ 0
Safe harbor payment	49,909,000
Revenue expected to be recognized from safe harbor prepayments	44,500,000
Envoy Communications Gateway
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue expected to be recognized from safe harbor prepayments	5,400,000
Letter of credit
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Line of credit	44,700,000
Collateralized letter of credit	$ 44,700,000

REVENUE RECOGNITION - Summary of Significant Changes in the Balances of Contract Liabilities and Assets (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Contract Assets
Balance, beginning of period	$ 47,664
Revenue recognized	(15,144)
Increase	24,622
Balance, end of period	57,142
Contract Liabilities
Balance, beginning of period	110,030
Revenue recognized	39,777
Increase due to billings	61,825
Increase due to safe harbor prepayments	49,909
Balance, end of period	$ 181,987

REVENUE RECOGNITION - Summary of Estimated Revenue Expected to be Recognized in Future Periods (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Revenue from Contract with Customer [Abstract]
Total estimated revenue expected to be recognized in future periods	$ 181,987
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue from Contract with Customer [Abstract]
Total estimated revenue expected to be recognized in future periods	$ 81,783
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total estimated revenue expected to be recognized in future periods, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue from Contract with Customer [Abstract]
Total estimated revenue expected to be recognized in future periods	$ 30,665
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total estimated revenue expected to be recognized in future periods, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue from Contract with Customer [Abstract]
Total estimated revenue expected to be recognized in future periods	$ 25,633
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total estimated revenue expected to be recognized in future periods, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue from Contract with Customer [Abstract]
Total estimated revenue expected to be recognized in future periods	$ 19,841
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total estimated revenue expected to be recognized in future periods, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue from Contract with Customer [Abstract]
Total estimated revenue expected to be recognized in future periods	$ 14,650
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total estimated revenue expected to be recognized in future periods, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue from Contract with Customer [Abstract]
Total estimated revenue expected to be recognized in future periods	$ 9,415
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total estimated revenue expected to be recognized in future periods, expected timing

INVENTORY - Summary of Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Raw materials	$ 4,197	$ 970
Finished goods	27,859	15,297
Total inventory	$ 32,056	$ 16,267

PROPERTY AND EQUIPMENT, NET Summary of Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 81,031	$ 72,895
Less accumulated depreciation and amortization	(52,095)	(51,897)
Property and equipment, net	$ 28,936	20,998
Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	3 years
Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	10 years
Equipment and machinery
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 48,114	43,566
Equipment and machinery \| Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	3 years
Equipment and machinery \| Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	10 years
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 2,404	2,239
Furniture and fixtures \| Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	5 years
Furniture and fixtures \| Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	10 years
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,698	2,958
Computer equipment \| Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	3 years
Computer equipment \| Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	5 years
Capitalized software costs
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 11,656	12,114
Capitalized software costs \| Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	3 years
Capitalized software costs \| Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	5 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 8,713	8,482
Leasehold improvements \| Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	3 years
Leasehold improvements \| Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	10 years
Construction in process
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 8,446	$ 3,536

PROPERTY AND EQUIPMENT, NET Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 7.3	$ 8.3	$ 8.6
Unamortized capitalized software costs	$ 0.8	$ 0.7

GOODWILL AND INTANGIBLE ASSETS - Schedule of Goodwill and Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Goodwill, Gross	$ 24,783	$ 24,783
Goodwill, Net	24,783	24,783
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Other indefinite-lived intangibles, Gross	286	286
Intangible assets with finite lives:
Gross	36,486	38,151
Accumulated Amortization	(5,907)	(2,845)
Net	30,579	35,306
Patents and licensed technology
Intangible assets with finite lives:
Gross	0	1,665
Accumulated Amortization	0	(1,665)
Net	0	0
Developed technology
Intangible assets with finite lives:
Gross	13,100	13,100
Accumulated Amortization	(3,093)	(909)
Net	10,007	12,191
Customer relationship
Intangible assets with finite lives:
Gross	23,100	23,100
Accumulated Amortization	(2,814)	(271)
Net	$ 20,286	$ 22,829

GOODWILL AND INTANGIBLE ASSETS - Amortization Expense (Details) - USD ($) $ in Thousands		12 Months Ended
	Aug. 09, 2018	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets		$ 4,727	$ 1,680
Amortization period for acquired intangible assets	15 years
Developed technology, and patents and licensed technology
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets		2,184	1,409
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets		$ 2,543	$ 271
SunPower’s
Finite-Lived Intangible Assets [Line Items]
Agreement for exclusive supplier rights, period	5 years
SunPower’s \| Developed technology, and patents and licensed technology
Finite-Lived Intangible Assets [Line Items]
Amortization period for acquired intangible assets	6 years
SunPower’s \| Customer relationships
Finite-Lived Intangible Assets [Line Items]
Amortization period for acquired intangible assets	9 years

ACCRUED LIABILITIES - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accrued Liabilities [Abstract]
Salaries, commissions, incentive compensation and benefits	$ 5,524	$ 4,107
Customer rebates and sales incentives	24,198	8,527
Freight	4,908	7,286
Operating lease liabilities, current	3,170
Other	9,292	9,090
Total accrued liabilities	$ 47,092	$ 29,010

WARRANTY OBLIGATIONS - Summary of Warranty Activities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Changes in the Company's product warranty liability
Warranty obligations, beginning of period	$ 31,294	$ 29,816	$ 31,414
Accruals for warranties issued during period	5,244	3,040	3,797
Changes in estimates	8,591	6,515	(732)
Settlements	(10,881)	(8,579)	(7,037)
Increase due to accretion expense	2,326	1,989	2,053
Other	524	(1,487)	321
Warranty obligations, end of period	37,098	31,294	29,816
Less: current portion	(10,078)	(8,083)	(7,427)
Noncurrent	$ 27,020	$ 23,211	$ 22,389

WARRANTY OBLIGATIONS - Narrative (Details) microinverter in Millions, $ in Millions	12 Months Ended			36 Months Ended	144 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2019 microinverter	Dec. 31, 2019 microinverter
Increased U.S. tariffs for products manufactured in China
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in variables	$ 5.5
Backwards compatibility cables
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in variables		$ 0.9
Claim rates
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in variables		2.1
Labor reimbursement cost
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in variables		0.2
Discount rate
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in variables		(1.5)
IQ Series
Product Liability Contingency [Line Items]
Number of units sold \| microinverter				9.6
Percent of total sales	98.00%
Prior Generations
Product Liability Contingency [Line Items]
Number of units sold \| microinverter					15.7
Second Generation
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in variables			$ (2.2)
Second Generation \| Failure rate
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in variables			3.9
Second Generation \| Labor reimbursement cost
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in variables			$ (1.9)
Second and Third Generations \| Failure rate
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in variables	$ 3.1	$ 3.3

FAIR VALUE MEASUREMENTS - Schedule of Liabilities Measured at Fair Value on a Recurring Basis (Details) - Recurring - Level 3 - Total warranty obligations measured at fair value - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warranty obligations, current	$ 6,794	$ 4,288
Warranty obligations, non-current	13,012	7,469
Obligations measured at fair value	$ 19,806	$ 11,757	$ 9,791	$ 10,332

FAIR VALUE MEASUREMENTS - Schedule of Changes in Nonfinancial Liabilities Related to Warrant Obligations Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Details) - Level 3 - Recurring - Total warranty obligations measured at fair value - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 11,757	$ 9,791	$ 10,332
Accruals for warranties issued during period	5,244	3,040	3,591
Changes in estimates	6,167	2,455	(4,551)
Settlements	(6,212)	(4,030)	(1,956)
Increase due to accretion expense	2,326	1,989	2,053
Other	524	(1,488)	322
Balance at end of period	$ 19,806	$ 11,757	$ 9,791

FAIR VALUE MEASUREMENTS - Summary of Significant Unobservable Inputs used in the Fair Value Measurement of Liabilities Designated as Level 3 (Details) - Recurring - Level 3 - Warranty obligations for microinverters sold since January 1, 2014	Dec. 31, 2019	Dec. 31, 2018
Profit element and risk premium
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warranty obligations for microinverters sold since January 1, 2014	0.14	0.16
Credit-adjusted risk-free rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warranty obligations for microinverters sold since January 1, 2014	0.16	0.19

FAIR VALUE MEASUREMENTS - Narrative (Details) $ in Millions	12 Months Ended
FAIR VALUE MEASUREMENTS - Narrative (Details) $ in Millions	Dec. 31, 2019 USD ($)
Fair Value Disclosures [Abstract]
Increase in liability as a result of increasing the profit element and risk premium input by 100 basis points	$ 0.2
Decrease in liability as a result of decreasing the profit element and risk premium input by 100 basis points	0.2
Decrease in liability as a result of increasing the discount rate by 100 basis points	0.8
Increase in liability as a result of decreasing the discount rate by 100 basis points	$ 0.9

RESTRUCTURING - Summary of Restructuring Charges (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 1,131	$ 469	$ 631	$ 368	$ 1,541	$ 2,588	$ 0	$ 0	$ 2,599	$ 4,129	$ 16,917
Asset impairment charges									1,100	1,600	800
Redundancy and employee severance and benefit arrangements
Restructuring Cost and Reserve [Line Items]
Restructuring charges									1,575	2,228	2,827
Asset impairments
Restructuring Cost and Reserve [Line Items]
Asset impairment charges									1,124	1,601	522
Consultants engaged in restructuring activities
Restructuring Cost and Reserve [Line Items]
Restructuring charges									0	0	12,100
Lease loss reserves
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, accrual adjustment									(100)	300	$ 1,468
Restructuring Plan 2018
Restructuring Cost and Reserve [Line Items]
Restructuring charges									2,599	4,204
Restructuring Plan 2018 \| Redundancy and employee severance and benefit arrangements
Restructuring Cost and Reserve [Line Items]
Restructuring charges									1,575	2,228
Restructuring Plan 2018 \| Asset impairments
Restructuring Cost and Reserve [Line Items]
Restructuring charges									1,124	1,636
Restructuring Plan 2018 \| Lease loss reserves
Restructuring Cost and Reserve [Line Items]
Restructuring charges									$ (100)	$ 340

RESTRUCTURING - Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Restructuring Plan 2018
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning	$ 1,192
Charges	2,699
Cash payments	(1,610)
Non-cash settlement and other	(2,281)
Restructuring reserve, ending	0	$ 1,192
Restructuring Plan 2018 \| Redundancy and Employee Severance and Benefits
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning	904
Charges	2,699
Cash payments	(1,610)
Non-cash settlement and other	(1,993)
Restructuring reserve, ending	0	904
Restructuring Plan 2018 \| Lease Loss Reserves and Contractual Obligations
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning	288
Charges	0
Cash payments	0
Non-cash settlement and other	(288)
Restructuring reserve, ending	0	288
Restructuring Plan 2016
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning	1,591	1,323
Charges		(40)
Cash payments		308
Non-cash settlement and other	(1,591)
Restructuring reserve, ending	0	1,591
Restructuring Plan 2016 \| Redundancy and Employee Severance and Benefits
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning	0	229
Charges		0
Cash payments		(229)
Non-cash settlement and other	0
Restructuring reserve, ending	0	0
Restructuring Plan 2016 \| Lease Loss Reserves and Contractual Obligations
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning	1,591	1,094
Charges		(40)
Cash payments		537
Non-cash settlement and other	(1,591)
Restructuring reserve, ending	$ 0	$ 1,591

DEBT - Long-term debt (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Total carrying amount of debt	$ 105,543	$ 109,783
Debt, current	(2,884)	(28,155)
Long-term debt	102,659	81,628
Convertible Notes \| Convertible Senior Note Due 2024
Debt Instrument [Line Items]
Long-term debt, gross	132,000	0
Less unamortized discount and issuance costs	(35,815)	0
Total carrying amount of debt	96,185	0
Convertible Notes \| Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Long-term debt, gross	5,000	65,000
Total carrying amount of debt	4,857	62,639
Less: unamortized issuance costs	(143)	(2,361)
Secured Debt \| Term Loan Agreement, July 2016
Debt Instrument [Line Items]
Long-term debt, gross	0	41,524
Less unamortized discount and issuance costs	0	(1,059)
Total carrying amount of debt	0	40,465
Debt, current	0	(25,417)
Financing Receivable \| Financing Receivable Recorded as Debt
Debt Instrument [Line Items]
Long-term debt, gross	4,501	6,679
Debt, current	$ (2,884)	$ (2,738)

DEBT - Convertible Senior Notes due 2024 (Details) $ / shares in Units, shares in Millions		12 Months Ended
	Jun. 05, 2019 USD ($) trading_day $ / shares shares	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Deferred tax assets, net		$ 74,531,000	$ 0
Payment for bonds hedge		36,313,000	0	$ 0
Proceeds from sale of warrants	$ 29,800,000	$ 29,818,000	$ 0	$ 0
Convertible Notes \| Convertible Senior Note Due 2024
Debt Instrument [Line Items]
Debt instrument face amount	$ 132,000,000.0
Interest rate	1.00%
Debt conversion price (in USD per share) \| $ / shares	$ 20.5010
Proceeds from convertible debt	$ 128,000,000.0
Convertible note, liability component	$ 95,600,000
Effective percentage rate	7.75%	7.75%
Convertible note, equity component	$ 36,400,000
Deferred tax assets, net		$ 300,000
Debt issuance costs	4,600,000
Unamortized debt issuance costs	3,300,000	2,900,000
Debt issuance costs, allocated to capital	$ 1,300,000
Unamortized discount		$ 32,900,000
Remaining discount amortization period		4 years 4 months 24 days
Warrants sold (in shares) \| shares	6.4
Warrants issued, strike price (in USD per share) \| $ / shares	$ 25.2320
Conversion ratio	0.0487781
Conversion shares (in shares) \| shares	6.4
Period One \| Convertible Notes \| Convertible Senior Note Due 2024
Debt Instrument [Line Items]
Number of threshold trading days \| trading_day	20
Number of consecutive trading days \| trading_day	30
Stock trigger price (in USD per share) \| $ / shares	$ 26.6513
Threshold percentage	130.00%
Measurement period percentage of stock price trigger	98.00%
Period Two \| Convertible Notes \| Convertible Senior Note Due 2024
Debt Instrument [Line Items]
Threshold percentage	100.00%
Convertible Notes \| Level 2
Debt Instrument [Line Items]
Obligations measured at fair value		$ 190,900,000

DEBT - Schedule of Convertible Senior Notes due 2024 (Details) - Convertible Notes - Convertible Senior Note Due 2024 $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Debt Instrument [Line Items]
Contractual interest expense	$ 759
Amortization of debt discount (Premium)	3,492
Amortization of debt issuance costs	375
Total interest cost recognized	$ 4,626

DEBT - Convertible Senior Notes due 2023 (Details) - Convertible Senior Notes Due 2023		1 Months Ended	12 Months Ended
	Jun. 05, 2019 USD ($) shares	Aug. 31, 2018 USD ($) $ / shares	Dec. 31, 2019 USD ($)
Debt Instrument [Line Items]
Conversion shares (in shares) \| shares	10,801,080
Fees paid for repurchase and exchange of convertible notes	$ 6,000,000.0		$ 6,000,000.0
Convertible Notes
Debt Instrument [Line Items]
Debt instrument face amount		$ 65,000,000.0	5,000,000.0
Interest rate		4.00%
Debt converted	$ 60,000,000.0
Debt conversion price (in USD per share) \| $ / shares		$ 5.56
Redemption price percentage		100.00%
Conversion ratio		0.180018
Reclassification Adjustment \| Convertible Notes
Debt Instrument [Line Items]
Deferred issuance costs			2,000,000.0
Accrued interest			$ 800,000

DEBT - Schedule of Convertible Senior Notes due 2023 (Details) - Convertible Notes - Convertible Senior Notes Due 2023 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Contractual interest expense	$ 1,226	$ 975
Amortization of debt issuance costs	245	193
Total interest cost recognized	$ 1,471	$ 1,168

DEBT - Term Loan (Details) - USD ($)	Jan. 28, 2019	Feb. 28, 2017	Jul. 31, 2016
Debt Instrument [Line Items]
Repayments of debt	$ 39,500,000
Tennenbaum Capital Partners, LLC \| Secured Debt \| Amended Tennenbaum Capital Partners LLC Agreement
Debt Instrument [Line Items]
Debt instrument face amount		$ 25,000,000.0	$ 25,000,000.0

DEBT - Sale of Long - Term Financing Receivables (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Proceeds from debt, net of issuance costs		$ 0	$ 68,024	$ 26,442
Value of future purchase option	$ 700			$ 700
Financing Receivable \| Financing Receivable Recorded As Debt
Debt Instrument [Line Items]
Proceeds from debt, net of issuance costs	$ 2,800		$ 5,600

COMMITMENTS AND CONTINGENT LIABILITIES - Narrative (Details)	Dec. 31, 2019 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Term of lease contract, maximum renewal term	12 years
Purchase obligation	$ 99,500,000
Line of Credit Facility [Line Items]
Letters of credit outstanding	0
Letter of credit
Line of Credit Facility [Line Items]
Line of credit	44,700,000
Collateralized letter of credit	$ 44,700,000

COMMITMENTS AND CONTINGENT LIABILITIES - Lease Expense Components (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Operating lease costs	$ 4,041

COMMITMENTS AND CONTINGENT LIABILITIES - Lease Liabilities (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Operating lease liabilities, current (Accrued liabilities)	$ 3,170
Operating lease liabilities, noncurrent (Other liabilities)	9,542
Total operating lease liabilities	$ 12,712
Weighted average remaining lease term	5 years 6 months
Weighted average discount rate	8.60%

COMMITMENTS AND CONTINGENT LIABILITIES - Supplemental Cash Flow and Other Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Operating cash flows from operating leases	$ 3,636
Lease liabilities arising from obtaining right-of-use assets	$ 4,834

COMMITMENTS AND CONTINGENT LIABILITIES - Schedule of Minimum Lease Payments Under Noncancelable Operating Leases (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2020	$ 4,156
2021	4,238
2022	2,927
2023	2,188
2024	921
2025 and thereafter	740
Total lease payments	15,170
Less: imputed lease interest	(2,458)
Total lease liabilities	$ 12,712

COMMITMENTS AND CONTINGENT LIABILITIES - Non-cancelable Operating Leases (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2019	$ 3,738
2020	3,532
2021	3,276
2022	1,810
2023	945
Thereafter	1,252
Total	14,553
Sublease income to be recognized in the future under noncancelable subleases	(922)
Net operating lease minimum payments	$ 13,631

SALE OF COMMON STOCK (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions	1 Months Ended		12 Months Ended
	Feb. 28, 2018	Jan. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Subsidiary, Sale of Stock [Line Items]
Proceeds from issuance of common stock			$ 0	$ 19,766	$ 26,425
Private Placement
Subsidiary, Sale of Stock [Line Items]
Number of shares issued (in shares)	9.5
Price per share issued (in usd per share)	$ 2.10
Proceeds from issuance of common stock	$ 20,000
Common stock, shares issued (shares)		10.8
Gross proceeds from issuance of common stock		$ 10,000

STOCK-BASED COMPENSATION Narrative (Details)					3 Months Ended	12 Months Ended
STOCK-BASED COMPENSATION Narrative (Details)	Jan. 01, 2020 shares	May 18, 2017 shares	Mar. 01, 2017 shares	Mar. 29, 2012 shares	Mar. 31, 2019 $ / shares shares	Dec. 31, 2019 USD ($) purchase_period $ / shares shares	Dec. 31, 2018 $ / shares shares	Dec. 31, 2017 shares	Dec. 31, 2016 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, outstanding (in shares)						4,097,000	6,772,000	8,426,000	8,730,000
Total unrecognized compensation cost \| $						$ 31,500,000
Weighted-average recognition period for unrecognized compensation cost						2 years 3 months 18 days
Common stock to be purchased in exchange for options (in shares)						102,000	521,000	4,379,000
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance target percentage					0.00%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance target percentage					200.00%
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock to be purchased in exchange for options (in shares)			2,362,470
Performance shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award granted (in shares)					1,000,000.0	1,052,000	1,477,000
Weighted average estimated fair value of award (in usd per share) \| $ / shares						$ 9.48	$ 4.65
Performance shares without market conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average estimated fair value of award (in usd per share) \| $ / shares					$ 8.80
Performance shares with market conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award granted (in shares)					500,000
Weighted average estimated fair value of award (in usd per share) \| $ / shares					$ 10.70
Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock to be purchased in exchange for options (in shares)			733,559
Two Thousand Six Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, vesting period						4 years
Share-based compensation, weighted-average remaining contractual term						10 years
Share-based compensation, outstanding (in shares)						100,000
Two Thousand and Eleven Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, vesting period						4 years
Share-based compensation, shares authorized (in shares)						2,643,171
Increase in common stock shares reserved for future issuance percentage						4.50%
Share-based compensation, shares available for grant (in shares)						4,355,838
Employee Stock Purchase Plan (ESPP)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, shares authorized (in shares)				669,603
Share-based compensation, shares available for grant (in shares)						936,020
Share-based compensation, additional shares authorized (in shares)		400,000
Share-based compensation, evergreen shares (in shares)		700,000		330,396
Share-based compensation, increase in number of shares authorized				1.00%
Employee stock purchase plan, number of interim purchase periods \| purchase_period						4
General duration of employee stock purchase plan						24 months
Share-based compensation, maximum employee subscription rate						15.00%
Share-based compensation, purchase price of common stock percent to fair market value						85.00%
Share-based compensation, look-back feature (in years)						2 years
IRS limitation for employees right to acquire class common stock under ESPP \| $						$ 25,000
Before August 1, 2012 \| Two Thousand and Eleven Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, weighted-average remaining contractual term						10 years
After August 1, 2012 \| Two Thousand and Eleven Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, weighted-average remaining contractual term						7 years
Subsequent Event \| Two Thousand and Eleven Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, additional shares authorized (in shares)	5,539,886
Subsequent Event \| Employee Stock Purchase Plan (ESPP)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, evergreen shares (in shares)	700,000

STOCK-BASED COMPENSATION - Summary of the Weighted-Average Grant Date Fair Value of Options Granted (Details) - Stock options - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
The fair value of each option granted during the periods
Weighted average grant date fair value (in usd per share)	$ 9.16	$ 2.83	$ 0.76
Expected term	3 years 9 months 18 days	4 years	4 years 4 months 24 days
Expected volatility	89.10%	88.50%	83.90%
Annual risk-free rate of return	2.10%	2.60%	1.80%
Dividend yield	0.00%	0.00%	0.00%

STOCK-BASED COMPENSATION - Summary of the Components of Total Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 20,176	$ 11,432	$ 6,727
Total unrecognized compensation cost	$ 31,500
Weighted-average recognition period for unrecognized compensation cost	2 years 3 months 18 days
Cost of revenues
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 1,650	1,071	1,072
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	4,897	2,940	2,573
Sales and marketing
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	5,678	3,074	1,157
General and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	7,216	4,347	1,925
Restructuring
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 735	$ 0	$ 0

STOCK-BASED COMPENSATION - Summary of Stock-Based Compensation Associated with Each Type of Award (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 20,176	$ 11,432	$ 6,727
Stock options and RSUs and PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	19,216	10,691	5,559
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 960	$ 741	$ 1,168

STOCK-BASED COMPENSATION - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Number of Shares Outstanding
Outstanding, beginning balance (in shares)	6,772	8,426	8,730
Granted (in shares)	43	213	4,500
Exercised (in shares)	(2,616)	(1,346)	(425)
Canceled (in shares)	(102)	(521)	(4,379)
Outstanding, ending balance (in shares)	4,097	6,772	8,426
Shares outstanding, vested and expected to vest (in shares)	4,097
Shares outstanding, exercisable (in shares)	2,887
Weighted- Average Exercise Price per Share
Outstanding, beginning balance (in usd per share)	$ 1.76	$ 1.77	$ 4.55
Granted (in usd per share)	14.58	4.43	1.22
Exercised (in usd per share)	1.22	1.75	0.51
Canceled (in usd per share)	4.07	2.94	6.91
Outstanding, ending balance (in usd per share)	2.18	$ 1.76	$ 1.77
Weighted-average exercise price, vested and expected (in usd per share)	2.18
Weighted-average exercise price, exercisable (in usd per share)	$ 2.44
Weighted-Average Remaining Contractual Term
Outstanding	4 years 3 months 18 days
Vested and expected to vest	4 years 3 months 18 days
Exercisable	4 years 1 month 6 days
Aggregate Intrinsic Value
Exercised	$ 31,093	$ 5,096	$ 544
Outstanding	98,103
Vested and expected to vest	98,103
Exercisable	$ 68,397
Share price (in USD per share)	$ 26.13

STOCK-BASED COMPENSATION - Summary of Stock Options Outstanding (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2019 $ / shares shares
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options outstanding, number of shares (shares) \| shares	4,097
Options outstanding - weighted- average remaining life	4 years 3 months 18 days
Options outstanding - weighted- average exercise price (usd per share)	$ 2.18
Options exercisable - number of shares exercisable (shares) \| shares	2,887
Options Exercisable - weighted-average exercise price (usd per share)	$ 2.44
$0.64 —– $1.11
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price range, lower limit (usd per share)	0.64
Exercise price range, upper limit (usd per share)	$ 1.11
Options outstanding, number of shares (shares) \| shares	774
Options outstanding - weighted- average remaining life	5 years
Options outstanding - weighted- average exercise price (usd per share)	$ 0.82
Options exercisable - number of shares exercisable (shares) \| shares	518
Options Exercisable - weighted-average exercise price (usd per share)	$ 0.78
$1.29 —– $1.29
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price range, lower limit (usd per share)	1.29
Exercise price range, upper limit (usd per share)	$ 1.29
Options outstanding, number of shares (shares) \| shares	1,000
Options outstanding - weighted- average remaining life	4 years 8 months 12 days
Options outstanding - weighted- average exercise price (usd per share)	$ 1.29
Options exercisable - number of shares exercisable (shares) \| shares	563
Options Exercisable - weighted-average exercise price (usd per share)	$ 1.29
$1.31 —– $1.31
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price range, lower limit (usd per share)	1.31
Exercise price range, upper limit (usd per share)	$ 1.31
Options outstanding, number of shares (shares) \| shares	1,309
Options outstanding - weighted- average remaining life	4 years 3 months 18 days
Options outstanding - weighted- average exercise price (usd per share)	$ 1.31
Options exercisable - number of shares exercisable (shares) \| shares	975
Options Exercisable - weighted-average exercise price (usd per share)	$ 1.31
$1.37 —– $7.50
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price range, lower limit (usd per share)	1.37
Exercise price range, upper limit (usd per share)	$ 7.68
Options outstanding, number of shares (shares) \| shares	867
Options outstanding - weighted- average remaining life	3 years 2 months 12 days
Options outstanding - weighted- average exercise price (usd per share)	$ 4.18
Options exercisable - number of shares exercisable (shares) \| shares	702
Options Exercisable - weighted-average exercise price (usd per share)	$ 4.57
$7.68 —– $14.58
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price range, lower limit (usd per share)	7.68
Exercise price range, upper limit (usd per share)	$ 14.58
Options outstanding, number of shares (shares) \| shares	147
Options outstanding - weighted- average remaining life	3 years 4 months 24 days
Options outstanding - weighted- average exercise price (usd per share)	$ 11.45
Options exercisable - number of shares exercisable (shares) \| shares	129
Options Exercisable - weighted-average exercise price (usd per share)	$ 11.02

STOCK-BASED COMPENSATION - Summary of Restricted Stock Unit Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Aggregate Intrinsic Value
Share price (in USD per share)	$ 26.13
Restricted stock units
Number of Shares Outstanding
Outstanding, beginning balance (in shares)	4,352	3,505	606
Granted (in shares)	2,112	3,152	5,418
Vested (in shares)	(1,707)	(1,399)	(885)
Canceled (in shares)	(494)	(906)	(1,634)
Outstanding, ending balance (in shares)	4,263	4,352	3,505
Number of shares outstanding, expected to vest (in shares)	4,263
Weighted Average Fair Value per Share at Grant Date
Outstanding, beginning balance (in usd per share)	$ 3.52	$ 2.03	$ 9.33
Granted (in usd per share)	11.50	4.45	1.46
Vested (in usd per share)	3.87	2.75	3.81
Canceled (in usd per share)	4.81	2.17	1.90
Outstanding, ending balance (in usd per share)	7.19	$ 3.52	$ 2.03
Weighted-Average Fair Value per Share at Grant Date, Expected to vest (in usd per share)	$ 7.19
Weighted-Average Remaining Contractual Term
Weighted- Average Remaining Contractual Term	1 year 3 months 18 days
Expected to vest	1 year 3 months 18 days
Aggregate Intrinsic Value
Vested	$ 27,156	$ 6,657	$ 932
Outstanding	111,387
Aggregate intrinsic value, expected to vest	$ 111,387

STOCK-BASED COMPENSATION - Summary of Performance Stock Unit Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Aggregate Intrinsic Value
Share price (in USD per share)		$ 26.13
Performance shares
Number of Shares Outstanding
Outstanding, beginning balance (in shares)	1,330	1,330	0
Granted (in shares)	1,000	1,052	1,477
Vested (in shares)		(1,063)	0
Canceled (in shares)		(364)	(147)
Outstanding, ending balance (in shares)		955	1,330
Weighted Average Fair Value per Share at Grant Date
Outstanding, beginning balance (in usd per share)	$ 4.66	$ 4.66
Granted (in usd per share)		9.48	$ 4.65
Vested (in usd per share)		4.62
Canceled (in usd per share)		5.16
Outstanding, ending balance (in usd per share)		$ 9.83	$ 4.66
Weighted-Average Remaining Contractual Term
Weighted- Average Remaining Contractual Term		2 months 12 days
Aggregate Intrinsic Value
Vested		$ 10,818
Outstanding		$ 24,952

STOCK-BASED COMPENSATION Summary of ESPP Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Payment Arrangement [Abstract]
Proceeds from common stock issued under ESPP	$ 1,692	$ 397	$ 313
Shares of common stock issued (shares)	315	439	478
Weighted-average price per share (usd per share)	$ 5.37	$ 0.90	$ 0.65

INCOME TAXES - Schedule of Domestic and Foreign Components of Loss before Provision for Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
United States									$ 85,520	$ (14,322)	$ (47,882)
Foreign									4,594	4,093	2,541
Income (loss) before income taxes	$ 44,421	$ 31,371	$ 11,209	$ 3,113	$ 1,285	$ (3,222)	$ (3,399)	$ (4,893)	$ 90,114	$ (10,229)	$ (45,341)

INCOME TAXES - Schedule of Provision for Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current:
Federal									$ 0	$ 0	$ 0
State									327	42	21
Foreign									1,589	1,233	1,224
Total									1,916	1,275	1,245
Deferred:
Federal									(56,959)	(35)	(1,092)
State									(17,458)	(21)	(21)
Foreign									1,467	179	(281)
Total									(72,950)	123	(1,394)
Income taxes (benefit) provision	$ (72,245)	$ 272	$ 591	$ 348	$ 576	$ 248	$ 339	$ 235	$ (71,034)	$ 1,398	$ (149)

INCOME TAXES - Narrative (Details) $ in Millions	3 Months Ended	12 Months Ended
INCOME TAXES - Narrative (Details) $ in Millions	Dec. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Operating Loss Carryforwards [Line Items]
Decrease in valuation allowance	$ 92.9
Increase to unrecognized tax benefits		$ 0.3
Federal
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	147.4	147.4
Federal \| Research tax credit carryforward
Operating Loss Carryforwards [Line Items]
Research tax credit carryforwards	12.4	12.4
State
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	78.9	78.9
State \| Research tax credit carryforward
Operating Loss Carryforwards [Line Items]
Research tax credit carryforwards	$ 11.3	$ 11.3

INCOME TAXES - Schedule of Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Income tax (benefit) provision at statutory federal rate									$ 18,929	$ (2,148)	$ (15,416)
State taxes, net of federal benefit									(17,197)	17	(64)
Change in valuation allowance									(71,300)	8,198	(20,571)
Foreign tax rate and tax law differential									1,206	313	(133)
Tax credits									(1,803)	(378)	(382)
Stock-based compensation									(8,072)	(953)	761
Other permanent items									31	235	479
Other nondeductible/nontaxable items									2,765	(5,112)	930
Uncertain tax positions									504	107	106
Tax law changes									0	0	34,141
GILTI									1,086	917	0
Section 162(m)									2,817	202	0
Income taxes (benefit) provision	$ (72,245)	$ 272	$ 591	$ 348	$ 576	$ 248	$ 339	$ 235	$ (71,034)	$ 1,398	$ (149)

INCOME TAXES - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Allowances and reserves	$ 10,726	$ 10,022
Net operating loss and tax credit carryforwards	54,369	71,568
Stock-based compensation	3,753	3,662
Deferred revenue	16,736	19,562
Fixed assets and intangibles	2,720	3,836
Sec. 163(j) interest carryforward	0	2,064
Other	1,109	2,084
Subtotal	89,413	112,798
Less valuation allowance	0	(98,631)
Total deferred tax assets, net of valuation allowance	89,413	14,167
Deferred tax liabilities:
Goodwill	(1,368)	(1,070)
Unremitted foreign earnings	(5)	(16)
Deferred cost of goods sold	(14,374)	(12,655)
Total deferred tax liabilities	(15,747)	(13,741)
Net deferred tax asset	$ 73,666	$ 426

INCOME TAXES - Schedule of Reconciliation of Total Amounts of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits—at beginning of year	$ 6,325	$ 6,106	$ 6,016
Decreases in balances related to tax positions taken in prior years	(370)	0	(135)
Increases in balances related to tax positions taken in current year	771	329	306
Lapses in statutes of limitations	(137)	(110)	(81)
Unrecognized tax benefits—at end of year	$ 6,589	$ 6,325	$ 6,106

CONCENTRATION OF CREDIT RISK AND MAJOR CUSTOMERS (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts Receivable, Largest Customer \| Accounts receivable \| Credit concentration risk
Revenue, Major Customer [Line Items]
Percentage of concentration risk	34.00%	22.00%
Accounts Receivable, Second Largest Customer \| Accounts receivable \| Credit concentration risk
Revenue, Major Customer [Line Items]
Percentage of concentration risk	14.00%	13.00%
Accounts Receivable, Third Largest Customer \| Accounts receivable \| Credit concentration risk
Revenue, Major Customer [Line Items]
Percentage of concentration risk	11.00%
Net Revenues, Largest Customer \| Net revenue \| Customer concentration risk
Revenue, Major Customer [Line Items]
Percentage of concentration risk	21.00%	19.00%	15.00%
Net Revenue, Second Largest Customer \| Net revenue \| Customer concentration risk
Revenue, Major Customer [Line Items]
Percentage of concentration risk	12.00%		11.00%

NET INCOME (LOSS) PER SHARE - Schedule of Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net income (loss)	$ 116,666	$ 31,099	$ 10,618	$ 2,765	$ 709	$ (3,470)	$ (3,738)	$ (5,128)	$ 161,148	$ (11,627)	$ (45,192)
Notes due 2023 interest and financing costs, net									1,088	0	0
Adjusted net income (loss)									$ 162,236	$ (11,627)	$ (45,192)
Denominator:
Weighted average common shares outstanding (in shares)									116,713	99,619	82,939
Employee stock-based awards (in shares)									8,964	0	0
Warrants (in shares)									0	0	0
Weighted average common shares outstanding for diluted calculation (in shares)									131,644	99,619	82,939
Net income (loss) per share, basic (in USD per share)	$ 0.95	$ 0.25	$ 0.09	$ 0.03	$ 0.01	$ (0.03)	$ (0.04)	$ (0.06)	$ 1.38	$ (0.12)	$ (0.54)
Net income (loss) per share, diluted (in USD per share)	$ 0.88	$ 0.23	$ 0.08	$ 0.02	$ 0.01	$ (0.03)	$ (0.04)	$ (0.06)	$ 1.23	$ (0.12)	$ (0.54)
Convertible Notes \| Convertible Senior Note Due 2024
Denominator:
Notes due (in shares)									451	0	0
Convertible Notes \| Convertible Senior Notes Due 2023
Denominator:
Notes due (in shares)									5,516	0	0

NET INCOME (LOSS) PER SHARE - Schedule of Potentially Dilutive Securities Excluded from the Computation of Diluted Net Loss Per Share (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	485	24,684	12,545
Share-based Payment Arrangement, Option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	27	7,710	8,433
Employee stock-based awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	158	5,273	3,029
Warrant
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	300	0	1,083
Convertible Senior Notes Due 2023 \| Convertible Notes Payable
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	0	11,701	0

NET INCOME (LOSS) PER SHARE Narrative (Details)	Jun. 05, 2019 $ / shares
Convertible Senior Note Due 2024 \| Convertible Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Debt conversion price (in USD per share)	$ 20.5010

SEGMENT AND GEOGRAPHIC INFORMATION - Narrative (Details)	12 Months Ended
	Dec. 31, 2019 segment
Segment Reporting [Abstract]
Number of reportable segments	1
Number of operating segments	1

SEGMENT AND GEOGRAPHIC INFORMATION - Summary of Net Revenues by Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues	$ 210,032	$ 180,057	$ 134,094	$ 100,150	$ 92,289	$ 78,002	$ 75,896	$ 69,972	$ 624,333	$ 316,159	$ 286,166
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									523,577	219,600	199,565
International
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									$ 100,756	$ 96,559	$ 86,601

SEGMENT AND GEOGRAPHIC INFORMATION - Summary of Long-Lived Assets by Geographic Region (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 28,936	$ 20,998
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	16,754	13,146
China
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	4,635	5,504
Mexico
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	3,510	0
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 4,037	$ 2,348

RELATED PARTY Narrative (Details) - USD ($) shares in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Aug. 31, 2018
Related Party Transaction [Line Items]
Safe harbor payment		$ 49,909,000
SunPower’s
Related Party Transaction [Line Items]
Common stock held by related party (in shares)		6.5	7.5
Revenue from related parties		$ 70,900,000	$ 12,400,000
Accounts receivable, related parties	$ 15,900,000	15,900,000	10,300,000
Safe harbor payment	5,200,000
Convertible Notes \| Convertible Senior Notes Due 2023
Related Party Transaction [Line Items]
Debt instrument face amount	5,000,000.0	5,000,000.0		$ 65,000,000.0
Thurman John Rodgers \| Convertible Notes \| Convertible Senior Notes Due 2023
Related Party Transaction [Line Items]
Debt instrument face amount	$ 5,000,000	$ 5,000,000	$ 5,000,000.0

ACQUISITION - Narrative (Details) $ in Thousands, shares in Millions		12 Months Ended
	Aug. 09, 2018 USD ($) shares	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Business Acquisition [Line Items]
Goodwill		$ 24,783	$ 24,783
Amortization period for acquired intangible assets	15 years
Cash purchase price allocated in cash flows from operating activities		(14,788)	(19,151)	$ (4,121)
Cash purchase price allocated in cash flows from investing activities		139,067	16,132	(28,442)
Acquisition funded by issuance of common stock		$ 0	19,219	$ 0
SunPower’s
Business Acquisition [Line Items]
Agreement for exclusive supplier rights, period	5 years
Consideration transfered for business acquisition	$ 57,319
Common stock issued for business acquisition (in shares) \| shares	7.5
Issuance of Common Stock	$ 32,319
Limitation for trade or transfer, period	6 months
Limitation for number of shares to be transfered by acquiree, period	6 months
Goodwill	$ 21,119
Cash purchase price allocated in cash flows from operating activities			10,000
Cash Purchase Price	$ 25,000		25,000
Cash purchase price allocated in cash flows from investing activities			15,000
Acquisition funded by issuance of common stock			19,200
Total acquisition related costs			800
SunPower’s \| Developed technology
Business Acquisition [Line Items]
Amortization period for acquired intangible assets	6 years
SunPower’s \| Customer relationship
Business Acquisition [Line Items]
Consideration transfered for business acquisition	$ 23,100
Issuance of Common Stock	$ 13,100
Amortization period for acquired intangible assets	9 years
Cash Purchase Price	$ 10,000
SunPower’s \| Developed Technology And Goodwill
Business Acquisition [Line Items]
Consideration transfered for business acquisition	34,219
Issuance of Common Stock	19,219
Cash Purchase Price	$ 15,000		$ 15,000
Discount rate \| SunPower’s \| Minimum
Business Acquisition [Line Items]
Equity, measurement input	0.14
Discount rate \| SunPower’s \| Maximum
Business Acquisition [Line Items]
Equity, measurement input	0.30

ACQUISITION - Summary of Consideration Transfered for Business Acquisition (Details) - SunPower’s - USD ($) $ in Thousands		12 Months Ended
	Aug. 09, 2018	Dec. 31, 2018
Business Acquisition [Line Items]
Cash consideration	$ 25,000	$ 25,000
Common stock issued	32,319
Total	$ 57,319
Concentration Risk, Percentage	100.00%
Developed technology and goodwill
Business Acquisition [Line Items]
Cash consideration	$ 15,000	$ 15,000
Common stock issued	19,219
Total	$ 34,219
Concentration Risk, Percentage	60.00%
Customer relationship
Business Acquisition [Line Items]
Cash consideration	$ 10,000
Common stock issued	13,100
Total	$ 23,100
Concentration Risk, Percentage	40.00%

ACQUISITION - Summary of Fair Values of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Aug. 09, 2018
Business Acquisition [Line Items]
Goodwill	$ 24,783	$ 24,783
SunPower’s
Business Acquisition [Line Items]
Intangible assets			$ 36,200
Goodwill			21,119
Net assets acquired			$ 57,319

ACQUISITION - Summary of Identifiable Intangible Assets Acquired (Details) $ in Thousands	Aug. 09, 2018 USD ($)
Business Acquisition [Line Items]
Useful Life	15 years
SunPower’s
Business Acquisition [Line Items]
Intangible assets	$ 36,200
SunPower’s \| Developed technology
Business Acquisition [Line Items]
Intangible assets	$ 13,100
Useful Life	6 years
SunPower’s \| Customer relationship
Business Acquisition [Line Items]
Intangible assets	$ 23,100
Useful Life	9 years

SELECTED UNAUDITED QUARTERLY FINANCIAL INFORMATION - Schedule of Quarterly Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Net revenues	$ 210,032	$ 180,057	$ 134,094	$ 100,150	$ 92,289	$ 78,002	$ 75,896	$ 69,972	$ 624,333	$ 316,159	$ 286,166
Cost of revenues	132,151	115,351	88,775	66,811	64,124	52,738	53,195	51,657	403,088	221,714	230,123
Gross profit	77,881	64,706	45,319	33,339	28,165	25,264	22,701	18,315	221,245	94,445	56,043
Operating expenses:
Research and development	11,168	11,085	9,604	8,524	7,340	8,165	9,462	7,620	40,381	32,587	33,157
Sales and marketing	10,690	9,551	9,054	7,433	6,617	7,375	6,828	6,227	36,728	27,047	23,126
General and administrative	10,450	9,895	8,583	9,880	7,664	7,510	6,969	6,943	38,808	29,086	22,221
Restructuring charges	1,131	469	631	368	1,541	2,588	0	0	2,599	4,129	16,917
Total operating expenses	33,439	31,000	27,872	26,205	23,162	25,638	23,259	20,790	118,516	92,849	95,421
Income (loss) from operations	44,442	33,706	17,447	7,134	5,003	(374)	(558)	(2,475)	102,729	1,596	(39,378)
Interest income	815	894	593	211	490	321	154	93	2,513	1,058	276
Interest expense	(2,303)	(2,286)	(1,351)	(3,751)	(3,095)	(2,790)	(2,423)	(2,385)	(9,691)	(10,693)	(8,212)
Other income (expense)	1,467	(943)	(5,480)	(481)	(1,113)	(379)	(572)	(126)	(5,437)	(2,190)	1,973
Total other expense, net	(21)	(2,335)	(6,238)	(4,021)	(3,718)	(2,848)	(2,841)	(2,418)	(12,615)	(11,825)	(5,963)
Income before income taxes	44,421	31,371	11,209	3,113	1,285	(3,222)	(3,399)	(4,893)	90,114	(10,229)	(45,341)
Income tax benefit (provision)	72,245	(272)	(591)	(348)	(576)	(248)	(339)	(235)	71,034	(1,398)	149
Net income (loss)	$ 116,666	$ 31,099	$ 10,618	$ 2,765	$ 709	$ (3,470)	$ (3,738)	$ (5,128)	$ 161,148	$ (11,627)	$ (45,192)
Net income (loss) per share, basic (in USD per share)	$ 0.95	$ 0.25	$ 0.09	$ 0.03	$ 0.01	$ (0.03)	$ (0.04)	$ (0.06)	$ 1.38	$ (0.12)	$ (0.54)
Net income (loss) per share, diluted (in USD per share)	$ 0.88	$ 0.23	$ 0.08	$ 0.02	$ 0.01	$ (0.03)	$ (0.04)	$ (0.06)	$ 1.23	$ (0.12)	$ (0.54)

Label	Element	Value
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (38,948,000)
Additional Paid-in Capital [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	27,000
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	(38,948,000)
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (27,000)