Enphase Energy (ENPH) 10-Q 4 Aug 20 2020 Q2 Quarterly report Financial data

COVER PAGE

COVER PAGE - shares	6 Months Ended
	Jun. 30, 2020	Jul. 28, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2020
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 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 Common Stock, Shares Outstanding		126,007,389
Entity Central Index Key	0001463101
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Current Fiscal Year End	--12-31

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 607,254	$ 251,409
Restricted cash	0	44,700
Accounts receivable, net of allowances of $296 and $564 at June 30, 2020 and December 31, 2019, respectively	89,504	145,413
Inventory	31,186	32,056
Prepaid expenses and other assets	29,257	26,079
Total current assets	757,201	499,657
Property and equipment, net	32,972	28,936
Operating lease, right of use asset	11,462	10,117
Intangible assets, net	28,086	30,579
Goodwill	24,783	24,783
Other assets	49,551	44,620
Deferred tax assets, net	93,872	74,531
Total assets	997,927	713,223
Current liabilities:
Accounts payable	24,135	57,474
Accrued liabilities	46,691	47,092
Deferred revenues, current	40,256	81,783
Warranty obligations, current (includes $6,917 and $6,794 measured at fair value at June 30, 2020 and December 31, 2019, respectively)	10,170	10,078
Debt, current	102,271	2,884
Total current liabilities	223,523	199,311
Long-term liabilities:
Deferred revenues, noncurrent	110,977	100,204
Warranty obligations, noncurrent (includes $14,215 and $13,012 measured at fair value at June 30, 2020 and December 31, 2019, respectively)	27,737	27,020
Other liabilities	12,340	11,817
Debt, noncurrent	253,174	102,659
Total liabilities	627,751	441,011
Commitments and contingencies (Note 9)
Stockholders’ equity:
Common stock, $0.00001 par value, 200,000 shares and 150,000 shares authorized; and 125,979 shares and 123,109 shares issued and outstanding at June 30, 2020 and December 31, 2019, respectively	1	1
Additional paid-in capital	534,867	458,315
Accumulated deficit	(163,539)	(185,181)
Accumulated other comprehensive loss	(1,153)	(923)
Total stockholders’ equity	370,176	272,212
Total liabilities and stockholders’ equity	$ 997,927	$ 713,223

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Allowances, accounts receivable	$ 296	$ 564
Warranty obligations, current at fair value	6,917	6,794
Warranty obligations, non-current at fair value	$ 14,215	$ 13,012
Common stock, par value (in usd per share)	$ 0.00001	$ 0.00001
Common stock, shares authorized (in shares)	200,000,000	150,000,000
Common stock, shares issued (in shares)	125,979,000	123,109,000
Common stock, shares outstanding (in shares)	125,979,000	123,109,000

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Net revenues	$ 125,538	$ 134,094	$ 331,083	$ 234,244
Cost of revenues	77,151	88,775	202,021	155,586
Gross profit	48,387	45,319	129,062	78,658
Operating expenses:
Research and development	13,192	9,604	25,068	18,128
Sales and marketing	12,371	9,054	24,143	16,487
General and administrative	11,970	8,583	24,285	18,463
Restructuring charges	0	631	0	999
Total operating expenses	37,533	27,872	73,496	54,077
Income from operations	10,854	17,447	55,566	24,581
Other expense, net
Interest income	282	593	1,373	804
Interest expense	(5,952)	(1,351)	(9,107)	(5,102)
Other (expense) income, net	653	(5,480)	(271)	(5,961)
Change in fair value of derivatives	(59,692)	0	(44,348)	0
Total other expense, net	(64,709)	(6,238)	(52,353)	(10,259)
Income (loss) before income taxes	(53,855)	11,209	3,213	14,322
Income tax benefit (provision)	6,561	(591)	18,429	(939)
Net income (loss)	$ (47,294)	$ 10,618	$ 21,642	$ 13,383
Net income (loss) per share:
Basic (in USD per share)	$ (0.38)	$ 0.09	$ 0.17	$ 0.12
Diluted (in USD per share)	$ (0.38)	$ 0.08	$ 0.16	$ 0.11
Shares used in per share calculation:
Basic (in shares)	125,603	113,677	124,567	110,951
Diluted (in shares)	125,603	130,737	138,910	129,400

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (47,294)	$ 10,618	$ 21,642	$ 13,383
Other comprehensive loss:
Foreign currency translation adjustments	(62)	(249)	(230)	(328)
Comprehensive income (loss)	$ (47,356)	$ 10,369	$ 21,412	$ 13,055

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDER'S EQUITY - USD ($) $ in Thousands	Total	Common Stock and Additional Paid-In Capital	Accumulated deficit	Accumulated Other Comprehensive Income (Loss)	Cumulative Effect, Period of Adoption, AdjustmentCommon Stock and Additional Paid-In Capital	[1]	Cumulative Effect, Period of Adoption, AdjustmentAccumulated deficit	[1]
Balance, beginning of period at Dec. 31, 2018		$ 353,336	$ (346,302)	$ 742	$ 27		$ (27)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from exercise of equity awards		2,622
Payment of withholding taxes related to net share settlement of equity awards		(2,090)
Conversion of convertible notes due 2023, net		58,857
Equity component of convertible notes		35,089
Cost of convertible notes hedge related to the convertible notes		(36,313)
Sale of warrants related to the convertible notes		29,818
Stock-based compensation expense and other		8,457
Net income (loss)	$ 13,383		13,383
Foreign currency translation adjustments	(328)			(328)
Balance, end of period at Jun. 30, 2019	$ 117,271	449,803	(332,946)	414
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201807Member
Balance, beginning of period at Mar. 31, 2019		357,024	(343,563)	663	1		(1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from exercise of equity awards		958
Payment of withholding taxes related to net share settlement of equity awards		(735)
Conversion of convertible notes due 2023, net		58,857
Equity component of convertible notes		35,089
Cost of convertible notes hedge related to the convertible notes		(36,313)
Sale of warrants related to the convertible notes		29,818
Stock-based compensation expense and other		5,104
Net income (loss)	$ 10,618		10,618
Foreign currency translation adjustments	(249)			(249)
Balance, end of period at Jun. 30, 2019	$ 117,271	449,803	(332,946)	414
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201807Member
Balance, beginning of period at Dec. 31, 2019	$ 272,212	458,316	(185,181)	(923)	0		0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from exercise of equity awards		4,846
Payment of withholding taxes related to net share settlement of equity awards		(43,652)
Conversion of convertible notes due 2023, net		0
Equity component of convertible notes		116,300
Cost of convertible notes hedge related to the convertible notes		(117,108)
Sale of warrants related to the convertible notes		96,351
Stock-based compensation expense and other		19,815
Net income (loss)	21,642		21,642
Foreign currency translation adjustments	(230)			(230)
Balance, end of period at Jun. 30, 2020	$ 370,176	534,868	(163,539)	(1,153)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201807Member
Balance, beginning of period at Mar. 31, 2020		433,543	(116,245)	(1,091)	$ 0		$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from exercise of equity awards		2,867
Payment of withholding taxes related to net share settlement of equity awards		(9,385)
Conversion of convertible notes due 2023, net		0
Equity component of convertible notes		116,300
Cost of convertible notes hedge related to the convertible notes		(117,108)
Sale of warrants related to the convertible notes		96,351
Stock-based compensation expense and other		12,300
Net income (loss)	$ (47,294)		(47,294)
Foreign currency translation adjustments	(62)			(62)
Balance, end of period at Jun. 30, 2020	$ 370,176	$ 534,868	$ (163,539)	$ (1,153)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201807Member
[1]	Includes the adoption of Accounting Standards Update (“ASU”) 2018-07, “Compensation - Stock Compensation: Improvements to Non-employee Share-Based Payment Accounting” on January 1, 2019

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Cash flows from operating activities:
Net income	$ (47,294)	$ 10,618	$ 21,642	$ 13,383
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			7,985	7,694
Provision for doubtful accounts	81		185	207
Non-cash interest expense			8,094	2,266
Financing fees on extinguishment of debt			0	2,152
Fees paid for repurchase and exchange of convertible notes due 2023			0	6,000
Stock-based compensation			19,815	8,224
Change in fair value of derivatives	59,692	0	44,348	0
Deferred income taxes			(19,567)	0
Changes in operating assets and liabilities:
Accounts receivable			56,166	(19,104)
Inventory			870	(3,827)
Prepaid expenses and other assets			(9,534)	(9,568)
Accounts payable, accrued and other liabilities			(35,389)	16,805
Warranty obligations			809	1,699
Deferred revenues			(30,771)	5,904
Net cash provided by operating activities			64,653	31,835
Cash flows from investing activities:
Purchases of property and equipment			(7,804)	(3,176)
Net cash used in investing activities			(7,804)	(3,176)
Cash flows from financing activities:
Issuance of convertible notes, net of issuance costs			312,420	128,040
Purchase of convertible note hedges			(89,056)	(36,313)
Sale of warrants			71,552	29,819
Fees paid for repurchase and exchange of convertible notes due 2023			0	(6,000)
Principal payments and financing fees on debt			(1,633)	(45,122)
Proceeds from exercise of equity awards and employee stock purchase plan			4,846	2,622
Payment of withholding taxes related to net share settlement of equity awards			(43,652)	(2,090)
Net cash provided by financing activities			254,477	70,956
Effect of exchange rate changes on cash and cash equivalents			(181)	107
Net increase in cash and cash equivalents			311,145	99,722
Cash, cash equivalents and restricted cash—Beginning of period			296,109	106,237	$ 106,237
Cash and cash equivalents—End of period	$ 607,254	$ 205,959	607,254	205,959	296,109
Supplemental disclosures of non-cash investing and financing activities:
Purchases of fixed assets included in accounts payable			1,636	$ 1,194
Accrued interest payable unpaid upon exchange of convertible notes due 2023			$ 0		$ 833

DESCRIPTION OF BUSINESS AND BAS

DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION	6 Months Ended
	Jun. 30, 2020
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 condensed consolidated financial statements are presented in accordance with accounting principles generally accepted in the United States (“U.S.”), or GAAP. The condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Unaudited Interim Financial Information These accompanying unaudited condensed consolidated financial statements have been prepared pursuant to the rules and regulations of the SEC for interim financial reporting. In the opinion of management, these unaudited condensed consolidated financial statements reflect all adjustments, consisting of normal recurring items, considered necessary to present fairly the Company’s financial condition, results of operations, comprehensive income (loss) , stockholders’ equity and cash flows for the interim periods indicated. The results of operations for the three and six months ended June 30, 2020 are not necessarily indicative of the operating results for the full year. 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, allowance for doubtful accounts, stock-based compensation, inventory valuation, accrued warranty obligations, fair value of debt derivatives, fair value of acquired intangible assets and goodwill, useful lives of acquired intangible assets and property and equipment, incremental borrowing rate for right-of-use assets and lease liability, legal contingencies, 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. The worldwide spread of the COVID-19 virus has resulted in a global slowdown of economic activity which decreased demand for a broad variety of goods and services, including from our customers, while also disrupting sales channels and marketing activities for an unknown period of time and may continue to create significant uncertainty in future operational and financial performance. The Company expects this to result in negative impact on its sales and its results of operations. In preparing the Company’s condensed consolidated financial statements in accordance with GAAP, the Company is required to make estimates, assumptions and judgments that affect the amounts reported in its financial statements and the accompanying disclosures. Estimates and assumptions about future events and their effects cannot be determined with certainty and therefore require the exercise of judgment. As of the date of issuance of these financial statements, the Company is not aware of any specific event or circumstance that would require the Company to update its estimates, judgments or revise the carrying value of its assets or liabilities. These estimates may change, as new events occur and additional information is obtained, and are recognized in the condensed consolidated financial statements as soon as they become known. Actual results could differ from those estimates and any such differences may be material to the Company’s financial statements. Summary of Significant Accounting Policies There have been no significant changes to the Company’s significant accounting policies in Note 2. “Summary of Significant Accounting Policies,” of the notes to consolidated financial statements included in Item 8 of the Company’s 2019 Annual Report on Form 10-K. Recently Adopted Accounting Pronouncements 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. The Company adopted the new standard effective January 1, 2020 on a prospective basis and the adoption of this guidance did not have a material impact on its 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 current expected credit loss (CECL) model which will result in earlier recognition of credit losses. On January 1, 2020, the Company on a prospective basis adopted Topic 326, the measurement of expected credit losses under the CECL model is applicable to financial assets measured at amortized cost, including accounts receivable. The adoption of this guidance did not have a material impact on the Company’s consolidated financial statements.

REVENUE RECOGNITION

REVENUE RECOGNITION	6 Months Ended
	Jun. 30, 2020
Revenue from Contract with Customer [Abstract]
REVENUE RECOGNITION	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: Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Primary geographical markets: United States $ 100,791 $ 99,909 $ 280,391 $ 177,595 International 24,747 34,185 50,692 56,649 Total $ 125,538 $ 134,094 $ 331,083 $ 234,244 Timing of revenue recognition: Products delivered at a point in time $ 114,299 $ 124,336 $ 308,978 $ 214,736 Products and services delivered over time 11,239 9,758 22,105 19,508 Total $ 125,538 $ 134,094 $ 331,083 $ 234,244 Contract Balances Receivables, and contract assets and contract liabilities from contracts with customers are as follows: June 30, December 31, (In thousands) Receivables $ 89,504 $ 145,413 Short-term contract assets (Prepaid expenses and other assets) 16,416 15,055 Long-term contract assets (Other assets) 46,960 42,087 Short-term contract liabilities (Deferred revenues) 40,256 81,783 Long-term contract liabilities (Deferred revenues) 110,977 100,204 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. The Company had no asset impairment charges related to contract assets in the three and six months ended June 30, 2020 . 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, 2019 $ 57,142 Amount recognized (8,439 ) Increase 14,673 Balance as of June 30, 2020 $ 63,376 Contract liabilities are recorded as deferred revenue on the accompanying condensed 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. Significant changes in the balances of contract liabilities (deferred revenues) during the period are as follows (in thousands): Contract Liabilities Balance on December 31, 2019 $ 181,987 Revenue recognized (66,841 ) Increase due to billings 36,087 Balance as of June 30, 2020 $ 151,233 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: June 30, (In thousands) Fiscal year: 2020 (remaining six months) $ 21,679 2021 36,389 2022 31,357 2023 25,564 2024 20,373 Thereafter 15,871 Total $ 151,233

OTHER FINANCIAL INFORMATION

OTHER FINANCIAL INFORMATION	6 Months Ended
	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Other Financial Information	OTHER FINANCIAL INFORMATION Accounts Receivable, Net The Company receives payments from customers based upon contractual billing schedules. Accounts receivable are recorded when the right to consideration becomes unconditional. Accounts receivable, net consist of the following: June 30, December 31, (In thousands) Accounts receivable $ 89,800 $ 145,977 Allowance for doubtful accounts (296 ) (564 ) Accounts receivable, net $ 89,504 $ 145,413 Allowance for Doubtful Accounts The Company maintains allowances for doubtful accounts for uncollectible accounts receivable. Management estimates anticipated losses from doubtful accounts based on financial health of customers, days past due, collection history and existing economic conditions. The following table sets forth activities in the allowance for doubtful accounts for the periods indicated. Three Months Ended Six Months Ended 2020 (In thousands) Balance, at beginning of the period $ 374 $ 564 Net charges to expenses 81 185 Write-offs, net of recoveries (159 ) (453 ) Balance, at end of the period $ 296 $ 296 Inventory Inventory consist of the following: June 30, December 31, (In thousands) Raw materials $ 5,800 $ 4,197 Finished goods 25,386 27,859 Total inventory $ 31,186 $ 32,056 Accrued Liabilities Accrued liabilities consist of the following: June 30, December 31, (In thousands) Salaries, commissions, incentive compensation and benefits $ 3,607 $ 5,524 Customer rebates and sales incentives 20,741 24,198 Freight 2,640 4,908 Operating lease liabilities, current 3,570 3,170 Other 16,133 9,292 Total accrued liabilities $ 46,691 $ 47,092

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS	6 Months Ended
	Jun. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND INTANGIBLE ASSETS	GOODWILL AND INTANGIBLE ASSETS The Company’s goodwill and purchased intangible assets as of June 30, 2020 and December 31, 2019 are as follows: June 30, 2020 December 31, 2019 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: Developed technology 13,100 (4,185 ) 8,915 13,100 (3,093 ) 10,007 Customer relationships 23,100 (4,215 ) 18,885 23,100 (2,814 ) 20,286 Total purchased intangible assets $ 36,486 $ (8,400 ) $ 28,086 $ 36,486 $ (5,907 ) $ 30,579 Amortization expense related to finite-lived intangible assets are as follows: Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Developed technology, and patents and licensed technology $ 546 $ 546 $ 1,092 $ 1,092 Customer relationships 700 635 1,401 1,271 Total amortization expense $ 1,246 $ 1,181 $ 2,493 $ 2,363 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 Corporation’s (“SunPower”) microinverter business in August 2018 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 .

WARRANTY OBLIGATIONS

WARRANTY OBLIGATIONS	6 Months Ended
	Jun. 30, 2020
Product Warranties Disclosures [Abstract]
WARRANTY OBLIGATIONS	WARRANTY OBLIGATIONS The Company’s warranty activities were as follows: Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Warranty obligations, beginning of period $ 37,501 $ 31,042 $ 37,098 $ 31,294 Accruals for warranties issued during period 766 1,312 2,290 2,170 Changes in estimates 1,748 699 3,425 1,503 Settlements (2,578 ) (2,206 ) (5,848 ) (4,502 ) Increase due to accretion expense 804 550 1,578 1,101 Other (334 ) 1,597 (636 ) 1,428 Warranty obligations, end of period 37,907 32,994 37,907 32,994 Less: current portion (10,170 ) (7,468 ) (10,170 ) (7,468 ) Noncurrent $ 27,737 $ 25,526 $ 27,737 $ 25,526 Changes in Estimates For the three and six months ended June 30, 2020 , the Company recorded additional warranty expense of $1.7 million and $3.4 million , respectively, based on continuing analysis of field performance data and diagnostic root-cause failure analysis primarily relating to its prior generation products.

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	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. Level 1. The Compa ny considers all highly liquid investments, such as certificates of deposit and money market instruments with maturities of three 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 and are within Level 1 of the fair value hierarchy because they are valued using quoted market prices for identical instruments in active markets. As of June 30, 2020 , cash and cash equivalents balance includes money market funds of $598.5 million . Level 2. Convertible Notes due 2025 Derivatives On March 9, 2020 , the Company issued $320 million aggregate principal amount of 0.25% convertible senior notes due 2025 (the “ Notes due 2025 ”). Concurrently with the issuance of Notes due 2025 , the Company entered into privately-negotiated convertible note hedge and warrant transactions which in combination are intended to reduce the potential dilution from the conversion of the Notes due 2025 . On May 20, 2020 , at the Company’s annual meeting of stockholders, the stockholders approved an amendment to its certificate of incorporation to increase the number of authorized shares of the Company’s common stock. As a result, the Company satisfied the share reservation condition (as defined in the relevant indenture associated with the Notes due 2025 ). The Company will now be able to settle the Notes due 2025 , convertible notes hedge and warrants through payment or delivery, as the case may be, of cash, shares of its common stock or a combination thereof, at the Company’s election. Accordingly, on May 20, 2020 , the embedded derivative liability, convertible notes hedge and warrants liability were remeasured at a fair value of $116.3 million , $117.1 million and $96.4 million , respectively, and were then reclassified to additional paid-in-capital in the condensed consolidated balance sheet in the second quarter of 2020 and are no longer remeasured as long as they continue to meet the conditions for equity classification. See Note 8 . “Debt” for additional information related to these transactions. The fair value of the Convertible notes embedded derivative was estimated using Binomial Lattice model and the fair value of Convertible notes hedge and Warrants liability was estimated using Black-Scholes-Merton model. The significant observable inputs, either directly or indirectly, and assumptions used in the models to calculate the fair value of the derivatives include the Company’s common stock price, exercise price of the derivatives, risk-free interest rate, volatility, annual coupon rate and remaining contractual term. Notes due 2025 and Notes due 2024 . The Company carries the Notes due 2025 and Notes due 2024 (as defined below) at face value less unamortized discount and issuance costs on its condensed consolidated balance sheets. The fair value of the Notes due 2025 and Notes due 2024 of $288.9 million and $350.5 million , respectively, was determined 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 2025 and Notes due 2024 to be a Level 2 measurement as they are not actively traded. Level 3 . Wa rranty Obligations. The following table presents the Company’s warranty obligation that were measured at fair value on a recurring basis and its categorization within the fair value hierarchy. June 30, December 31, 2019 (In thousands) Level 3 Level 3 Liabilities: Warranty obligations Current $ 6,917 $ 6,794 Non-current 14,215 13,012 Total warranty obligations measured at fair value 21,132 19,806 Total liabilities measured at fair value $ 21,132 $ 19,806 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. Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Balance at beginning of period $ 20,425 $ 12,065 $ 19,806 $ 11,757 Accruals for warranties issued during period 766 1,312 2,290 2,170 Changes in estimates 983 519 1,598 860 Settlements (1,511 ) (1,188 ) (3,504 ) (2,460 ) Increase due to accretion expense 804 550 1,578 1,101 Other (335 ) 1,598 (636 ) 1,428 Balance at end of period $ 21,132 $ 14,856 $ 21,132 $ 14,856 Quantitative and Qualitative Information about Level 3 Fair Value Measurements As of June 30, 2020 and December 31, 2019 , 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 June 30, December 31, Warranty obligations for microinverters sold since January 1, 2014 Discounted cash flows Profit element and risk premium 15% 14% Credit-adjusted risk-free rate 16% 16% 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 $0.9 million reduction of the liability. Decreasing the discount rate by 100 basis points would result in a $1.0 million increase to the liability.

RESTRUCTURING

RESTRUCTURING	6 Months Ended
	Jun. 30, 2020
Restructuring and Related Activities [Abstract]
RESTRUCTURING	RESTRUCTURING Restructuring expense consist of the following: Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Redundancy and employee severance and benefit arrangements $ — $ 631 $ — $ 1,099 Lease loss reserves — — — (100 ) Total restructuring charges $ — $ 631 $ — $ 999 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.

DEBT

DEBT	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
DEBT	DEBT The following table provides information regarding the Company’s long-term debt. June 30, December 31, (In thousands) Convertible notes Notes due 2025 $ 320,000 $ — Less: unamortized discount and issuance costs (72,000 ) — Carrying amount of Notes due 2025 248,000 — Notes due 2024 132,000 132,000 Less: unamortized discount and issuance costs (32,301 ) (35,815 ) Carrying amount of Notes due 2024 99,699 96,185 Notes due 2023 5,000 5,000 Less: unamortized issuance costs (122 ) (143 ) Carrying amount of Notes due 2023 4,878 4,857 Sale of long-term financing receivable recorded as debt 2,868 4,501 Total carrying amount of debt 355,445 105,543 Less: current portion of convertible notes and long-term financing receivable recorded as debt (102,271 ) (2,884 ) Long-term debt $ 253,174 $ 102,659 Convertible Senior Notes due 2025 On March 9, 2020 , the Company issued $320.0 million aggregate principal amount of the Notes due 2025 . The Notes due 2025 are general unsecured obligations and bear interest at an annual rate of 0.25% per year, payable semi-annually on March 1 and September 1 of each year, beginning September 1, 2020 . The Notes due 2025 are governed by an indenture between the Company and U.S. Bank National Association, as trustee. The Notes due 2025 will mature on March 1, 2025 , 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 2025 may be converted, under certain circumstances as described below, based on an initial conversion rate of 12.2637 shares of common stock per $1,000 principal amount (which represents an initial conversion price of $81.54 per share). The conversion rate for the Notes due 2025 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 $313.0 million in net proceeds, after deducting the initial purchasers’ discount, from the issuance of the Notes due 2025 . The Notes due 2025 may be converted prior to the close of business on the business day immediately preceding September 1, 2024 , in multiples of $1,000 principal amount, at the option of the holder only under the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on June 30, 2020 (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 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 September 1, 2024 until the close of business on the second scheduled trading day immediately preceding the maturity date of March 1, 2025 , 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 2025 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. For the period from March 9, 2020, the issuance date, through May 19, 2020, the number of authorized and unissued shares of the Company’s common stock that are not reserved for other purposes was less than the maximum number of underlying shares that would be required to settle the Notes due 2025 into equity. Accordingly, unless and until the Company had a number of authorized shares that were not issued or reserved for any other purpose that equaled or exceeded the maximum number of underlying shares (“share reservation condition”), the Company would be required to pay to the converting holder in respect of each $1,000 principal amount of notes being converted solely in cash in an amount equal to the sum of the daily conversion values for each of the 20 consecutive trading days during the related observation period. However, following satisfaction of the share reservation condition, the Company could settle conversions of notes through payment or delivery, as the case may be, of cash, shares of the Company’s common stock or a combination of cash and shares of its common stock, at the Company’s election. In accounting for the issuance of the Notes due 2025 , on March 9, 2020 , the conversion option of the Notes due 2025 was deemed an embedded derivative requiring bifurcation from the Notes due 2025 (“host contract”) and separate accounting as an embedded derivative liability, as a result of the Company not having the necessary number of authorized but unissued shares of its common stock available to settle the conversion option of the Notes due 2025 in shares. The proceeds from the Notes due 2025 were first allocated to the embedded derivative liability and the remaining proceeds were then allocated to the host contract. On March 9, 2020 , the carrying amount of the embedded derivative liability of $68.7 million representing the conversion option was determined using the Binomial Lattice model and the remaining $251.3 million was allocated to the host contract. The difference between the principal amount of the Notes due 2025 and the fair value of the host contract (the “debt discount”) is amortized to interest expense using the effective interest method over the term of the Notes due 2025 . On May 20, 2020 , at the Company’s annual meeting of stockholders, the stockholders approved an amendment to the Amended and Restated Certificate of Incorporation to increase the number of authorized shares of the Company’s common stock, par value $0.00001 per share, from 150,000,000 shares to 200,000,000 shares (the “Amendment”). The Amendment became effective upon filing with the Secretary of State of Delaware on May 20, 2020 . As a result, the Company satisfied the share reservation condition. The Company may now settle the Notes due 2025 and warrants issued in conjunction with the Notes due 2025 through payment or delivery, as the case may be, of cash, shares of its common stock or a combination of cash and shares of its common stock, at the Company’s election. Accordingly, on May 20, 2020 , the embedded derivative liability was remeasured at a fair value of $116.3 million and was then reclassified to additional paid-in-capital in the condensed consolidated balance sheet in the second quarter of 2020 and is no longer remeasured as long as it continues to meet the conditions for equity classification. The Company recorded the change in the fair value of the embedded derivative in other expense, net in the condensed consolidated statement of operations during the three and six months ended June 30, 2020 . The following table presents the fair value and the change in fair value for the convertible note embedded derivative (in thousands): Convertible note embedded derivative (In thousands) Fair value as of March 9, 2020 $ 68,700 Change in the fair value (23,600 ) Fair value as of March 31, 2020 45,100 Change in the fair value 71,200 Fair value as of May 20, 2020 $ 116,300 Debt issuance costs for the issuance of the Notes due 2025 were approximately $7.6 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 Notes due 2025 host contract. Transaction costs were recorded as debt issuance cost (presented as contra debt in the condensed consolidated balance sheet) and are being amortized to interest expense over the term of the Notes due 2025 . The following table presents the total amount of interest cost recognized relating to the Notes due 2025 : Three Months Ended Six Months Ended (In thousands) Contractual interest expense $ 200 $ 249 Amortization of debt discount 3,069 3,812 Amortization of debt issuance costs 381 468 Total interest cost recognized $ 3,650 $ 4,529 The derived effective interest rate on the Notes due 2025 host contract was determined to be 5.18% , which remain unchanged from the date of issuance. The remaining unamortized debt discount was $64.9 million as of June 30, 2020 , will be amortized over approximately 4.7 years . Notes due 2025 Hedge and Warrant Transactions In connection with the offering of the Notes due 2025 , the Company entered into privately-negotiated convertible note hedge transactions pursuant to which the Company has the option to purchase a total of approximately 3.9 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 $81.54 per share, which is the initial conversion price of the Notes due 2025 . The total cost of the convertible note hedge transactions was approximately $89.1 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 2025 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 June 30, 2020 , 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 3.9 million shares of the Company’s common stock (subject to anti-dilution adjustments) at an initial strike price of $106.94 per share. The Company received aggregate proceeds of approximately $71.6 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 2025 and to effectively increase the overall conversion price from $81.54 to $106.94 per share. The Warrants are only exercisable on the applicable expiration dates in accordance with the agreements relating to each of the Warrants . Subject to the other terms of the Warrants, the first expiration date applicable to the Warrants is June 1, 2025 , and the final expiration date applicable to the Warrants is September 23, 2025 . As of June 30, 2020 , the Warrants had not been exercised and remained outstanding. For the period from March 9, 2020, the issuance date of the convertible notes hedge and warrant transactions, through May 19, 2020, the number of authorized and unissued shares of the Company’s common stock that are not reserved for other purposes was less than the maximum number of underlying shares that will be required to settle the Notes due 2025 through the delivery of shares of the Company’s common stock. Accordingly, the convertibles note hedge and the warrant transactions could only be settled on net cash settlement basis. As a result the convertible note hedge and the warrants transaction were classified as a Convertible notes hedge asset and Warrants liability, respectively, in the condensed consolidated balance sheet and the change in fair value of derivatives was included in other expense, net in the condensed consolidated statement of operations . On May 20, 2020 , at the Company’s annual meeting of stockholders, the stockholders approved the Amendment, and as a result, the Convertible notes hedge asset and Warrants liabilities were remeasured at a fair value of $117.1 million and $96.4 million , respectively, and were then reclassified to additional paid-in-capital in the condensed consolidated balance sheet in the second quarter of 2020 and is no longer remeasured as long as they continue to meet the conditions for equity classification. The change in the fair value of the Convertible notes hedge asset and Warrants liability were recorded in other expense, net in the condensed consolidated statements of operations during the three and six months ended June 30, 2020 . The following table presents the fair value and the change in fair value for the Convertible notes hedge asset and Warrants liability: Convertible notes hedge Warrants liability (In thousands) Fair value as of March 9, 2020 $ 89,056 $ 71,552 Change in the fair value (41,171 ) (32,915 ) Fair value as of March 31, 2020 47,885 38,637 Change in the fair value 69,223 57,715 Fair value as of May 20, 2020 $ 117,108 $ 96,352 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 only 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. As of June 30, 2020 , the sale price of the Company’s common stock was greater than or equal to $26.6513 ( 130% of the notes conversion price) for at least 20 trading days (whether consecutive or not) during a period of 30 consecutive trading days preceding the quarter-ended June 30, 2020 . As a result, as of June 30, 2020 , the Notes due 2024 are convertible at the holders’ option through September 30, 2020 . Accordingly, the Company classified the net carrying amount of the Notes due 2024 of $99.7 million as Debt, current on the condensed consolidated balance sheet as of June 30, 2020 . 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 condensed 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 condensed 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 condensed 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 June 30, 2020 and December 31, 2019 , the unamortized deferred issuance cost for the Notes due 2024 was $2.6 million and $2.9 million , respectively, on the condensed consolidated balance sheets. The following table presents the total amount of interest cost recognized relating to the Notes due 2024 : Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Contractual interest expense $ 330 $ 92 $ 660 $ 92 Amortization of debt discount 1,621 416 3,183 416 Amortization of debt issuance costs 166 45 332 45 Total interest cost recognized $ 2,117 $ 553 $ 4,175 $ 553 The effective interest rate on the liability component Notes due 2024 was 7.75% for the three and six months ended June 30, 2020 , which remains unchanged from the date of issuance. The remaining unamortized debt discount was $29.7 million and $32.9 million as of June 30, 2020 and December 31, 2019 , respectively, will be amortized over approximately 3.9 years from June 30, 2020 . Notes due 2024 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 June 30, 2020 , and through the date of this quarterly report, 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 June 30, 2020 , and through the report date, the Warrants had not been exercised and remained outstanding. Given that the transactions meet certain accounting criteria, the Notes due 2024 hedge and the warrants transactions 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 both June 30, 2020 and 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. 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 . Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Contractual interest expense $ 50 $ 483 $ 100 $ 1,133 Amortization of debt issuance costs 10 96 20 225 Total interest costs recognized $ 60 $ 579 $ 120 $ 1,358 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 condensed consolidated balance sheets, and the total associated debt balance will be relieved by September 2021 as the underlying receivables are settled.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	6 Months Ended
	Jun. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES 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: Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Operating lease costs $ 1,280 $ 564 $ 2,502 $ 1,063 The components of lease liabilities are presented as follows: June 30, December 31, (In thousands) Operating lease liabilities, current (Accrued liabilities) $ 3,570 $ 3,170 Operating lease liabilities, noncurrent (Other liabilities) 10,202 9,542 Total operating lease liabilities $ 13,772 $ 12,712 Supplemental lease information: Weighted average remaining lease term 5.4 years 5.5 years Weighted average discount rate 8.3% 8.6% Supplemental cash flow and other information related to operating leases, are as follows: Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 1,145 $ 857 $ 2,159 $ 1,594 Non-cash investing activities: Lease liabilities arising from obtaining right-of-use assets $ — $ 4,834 $ 2,941 $ 4,834 Undiscounted cash flows of operating lease liabilities as of June 30, 2020 are as follows: Lease Amounts (In thousands) Year: 2020 (remaining six months) $ 2,307 2021 4,679 2022 3,365 2023 2,648 2024 1,445 2025 and thereafter 1,949 Total lease payments 16,393 Less: imputed lease interest (2,621 ) Total lease liabilities $ 13,772 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 June 30, 2020 , these purchase obligations totaled approximately $75.2 million . Letter of Credits The Company had a standby letter of credit in the aggregate amount of $44.7 million , primarily in connection with one of its customer contracts. The letter of credit served as a performance security for product delivered to the customer in the first quarter of 2020 and expired on April 30, 2020 . No amounts were drawn against this letter of credit. As of June 30, 2020 , the Company has no letter of credit outstanding. Litigation The Company is subject to various legal proceedings relating to claims arising out of its operations that have not been fully resolved. The outcome of litigation is inherently uncertain. If one or more legal matters were resolved against the Company in a reporting period for amounts above management’s expectations, the Company’s business, results of operations, financial position and cash flows for that reporting period could be materially adversely affected. As of August 4, 2020, the Company is not currently a party to any matters that the management expects will have an adverse material effect on the Company’s consolidated financial position, results of operations or cash flows. Contingencies Since late September 2018, the Company has paid tariffs imposed on its microinverters by the China Section 301 Tariff Actions (“Section 301 Tariffs”) taken by the Office of the United States Trade Representative (the “USTR”) . The Company has sought refunds on tariffs previously paid on certain microinverter products that fit the dimensions and weight limits within a Section 301 Tariff exclusion under U.S. note 20(ss)(40) to subchapter III of chapter 99 of the Harmonized Tariff Schedule of the United States (the “Tariff Exclusion”). There is no material impact on the Company’s condensed consolidated statements of operations for the three and six months ended June 30, 2020 . The Company expects there will be a material positive impact on the Company’s financial statements if all of the requested refunds are approved in the future, totaling approximately $39 million plus accrued interest. The Tariff Exclusion expires on August 7, 2020, and the Company has filed a comment with the USTR supporting an extension of the Tariff Exclusion. The Company continues to pay Section 301 Tariffs on its storage and communication products and other accessories imported from China which are not subject to the Tariff Exclusion.

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	6 Months Ended
	Jun. 30, 2020
Share-based Payment Arrangement [Abstract]
STOCK-BASED COMPENSATION	STOCK-BASED COMPENSATION 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 condensed consolidated statements of operations for the periods presented. Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Cost of revenues $ 1,337 $ 386 $ 1,943 $ 617 Research and development 3,263 1,128 5,182 1,844 Sales and marketing 3,610 1,360 5,552 2,359 General and administrative 4,090 1,729 7,138 3,017 Restructuring — 332 — 387 Total $ 12,300 $ 4,935 $ 19,815 $ 8,224 The following table summarizes the various types of stock-based compensation expense for the periods presented. Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Stock options, RSUs, and PSUs $ 11,557 $ 4,760 $ 18,634 $ 7,982 Employee stock purchase plan 743 175 1,181 242 Total $ 12,300 $ 4,935 $ 19,815 $ 8,224 As of June 30, 2020 , there was approximately $76.9 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 2.1 years . 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. Three Months Ended Six Months Ended 2020 2019 2020 2019 Weighted average grant date fair value $ 38.45 $ 9.16 $ 38.45 $ 9.16 Expected term (in years) 3.8 3.8 3.8 3.8 Expected volatility 86.4 % 89.1 % 86.4 % 89.1 % Annual risk-free rate of return 0.1 % 2.1 % 0.1 % 2.1 % 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. Equity Awards Activity Stock Options The following is a summary of stock option activity. Number of Weighted- Weighted- Aggregate (1) (In thousands) (Years) (In thousands) Outstanding at December 31, 2019 4,097 $ 2.18 Granted 11 64.17 Exercised (968 ) 2.08 $ 50,611 Canceled (75 ) 7.34 Outstanding at June 30, 2020 3,065 $ 2.30 4.0 $ 138,877 Vested and expected to vest at June 30, 2020 3,065 $ 2.30 3.0 $ 138,877 Exercisable at June 30, 2020 2,270 $ 2.37 3.9 $ 102,649 (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 June 30, 2020 is based on the closing price of the Company’s stock fair value on June 30, 2020 or the earlier of the last trading day prior to June 30, 2020 , if June 30, 2020 is a non-trading day. The Company’s stock fair value used in this computation was $47.57 per share. The following table summarizes information about stock options outstanding at June 30, 2020 . Options Outstanding Options Exercisable Range of Exercise Prices Number of Weighted- Weighted- Number of Weighted- (In thousands) (Years) (In thousands) $0.70 —– $1.11 706 4.6 $ 0.82 546 $ 0.80 $1.29 —– $1.29 1,000 4.2 1.29 687 1.29 $1.31 —– $1.31 709 3.8 1.31 500 1.31 $1.37 —– $14.58 639 3.2 5.60 536 6.22 $64.17 —– $64.17 11 6.9 64.17 1 64.17 Total 3,065 4.0 $ 2.30 2,270 $ 2.37 Restricted Stock Units The following is a summary of RSU activity. Number of Weighted- Weighted- Aggregate (1) (In thousands) (Years) (In thousands) Outstanding at December 31, 2019 4,263 $ 7.19 Granted 1,077 36.62 Vested (1,380 ) 6.60 $ 55,925 Canceled (66 ) 16.15 Outstanding at June 30, 2020 3,894 $ 15.39 1.24 $ 185,236 Expected to vest at June 30, 2020 3,894 $ 15.39 1.24 $ 185,236 (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 June 30, 2020 is based on the closing price of the Company’s stock on June 30, 2020 or the earlier of the last trading day prior to June 30, 2020 , if June 30, 2020 is a non-trading day. The Company’s stock fair value used in this computation was $47.57 per share. Performance Stock Units The following is a summary of PSU activity. Number of Weighted- Weighted- Aggregate (1) (In thousands) (Years) (In thousands) Outstanding at December 31, 2019 955 $ 9.83 Granted 974 30.45 Vested (1,450 ) 10.20 $ 52,144 Canceled — — Outstanding at June 30, 2020 479 $ 50.37 0.7 $ 22,777 (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 June 30, 2020 is based on the closing price of the Company’s stock on June 30, 2020 or the earlier of the last trading day prior to June 30, 2020 , if June 30, 2020 is a non-trading day. The Company’s stock fair value used in this computation was $47.57 per share.

INCOME TAXES

INCOME TAXES	6 Months Ended
	Jun. 30, 2020
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES For the three and six months ended June 30, 2020 , the Company’s income tax benefit of $6.6 million and $18.4 million , respectively, on a net loss before income taxes of $53.9 million and on a net income before income taxes of $3.2 million , respectively, calculated using the annualized effective tax rate method, was primarily due to tax deduction from employee stock compensation as a discrete event, partially offset by projected tax expense in the U.S. and foreign jurisdictions that are profitable. For the three and six months ended June 30, 2019 , the Company’s income tax provision of $0.6 million and $0.9 million , respectively, on income before income taxes of $11.2 million and $14.3 million , respectively, calculated using the discrete tax approach, was primarily related to income taxes attributable to its foreign operations. For the three and six months ended June 30, 2020 , in accordance with FASB guidance for interim reporting of income tax, the Company has computed its provision for income taxes based on a projected annual effective tax rate while excluding loss jurisdictions which cannot be benefited. The Company used the discrete tax approach in calculating the tax expense for the three and six months ended June 30, 2019 due to the fact that a relatively small change in the Company’s projected pre-tax net income (loss) could result in a volatile effective tax rate. Under the discrete method, the Company determines its tax (expense) benefit based upon actual results as if the interim period was an annual period. The tax provision recorded was primarily related to income taxes attributable to its foreign operations.

NET INCOME (LOSS) PER SHARE

NET INCOME (LOSS) PER SHARE	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
NET INCOME (LOSS) PER SHARE	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 , Warrants issued in conjunction with the Notes due 2024 , and from May 20, 2020 to the end of the reporting period, the Notes due 2025 and Warrants issued in conjunction with the Notes due 2025 . See Note 8. “Debt” for additional information. 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, Notes due 2024 , warrants issued in conjunction with the Notes due 2024 , Notes due 2025 , warrants issued in conjunction with the Notes due 2025 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. Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands, except per share data) Numerator: Net income (loss) $ (47,294 ) $ 10,618 $ 21,642 $ 13,383 Notes due 2023 interest and financing costs, net — 430 89 1,006 Adjusted net income (loss) $ (47,294 ) $ 11,048 $ 21,731 $ 14,389 Denominator: Shares used in basic per share amounts: Weighted average common shares outstanding 125,603 113,677 124,567 110,951 Shares used in diluted per share amounts: Weighted average common shares outstanding 125,603 113,677 124,567 110,951 Effect of dilutive securities: Employee stock-based awards — 8,326 7,449 8,240 Warrants (issued in conjunction with Notes due 2024) — — 2,641 — Notes due 2024 — — 3,353 — Notes due 2023 — 8,734 900 10,209 Weighted average common shares outstanding for diluted calculation 125,603 130,737 138,910 129,400 Basic and diluted net income (loss) per share Net income (loss) per share, basic $ (0.38 ) $ 0.09 $ 0.17 $ 0.12 Net income per share, diluted $ (0.38 ) $ 0.08 $ 0.16 $ 0.11 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. Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Employee stock-based awards 6,459 66 294 77 Warrants (issued in conjunction with Notes due 2024) 3,039 — — — Notes due 2024 3,677 — — — Warrants (issued in conjunction with Notes due 2025) 3,924 — 3,430 — Notes due 2025 2,771 — 2,031 — Notes due 2023 900 — — — Total 20,770 66 5,755 77 The Company had a net loss for the three months ended June 30, 2020 , hence all common stock issuable under stock options, RSUs, PSUs, and shares to be purchased under the ESPP, the Notes due 2023, the Notes due 2024 and, warrants issued in conjunction with the Notes due 2024, Notes due 2025 and warrants issued in conjunction with the Notes due 2025 were excluded because including such shares would have been antidilutive. Diluted earnings per share for the six months ended June 30, 2020 includes the dilutive effect of stock options, RSUs, PSUs, and shares to be purchased under the ESPP, the Notes due 2023 , the Notes due 2024 and warrants issued in conjunction with the Notes due 2024 . Certain common stock issuable under stock options, RSUs, PSUs, Notes due 2025 and warrants issued in conjunction with the Notes due 2025 have been omitted from the diluted net income per share calculation because including such shares would have been antidilutive. Diluted earnings per share for the three and six months ended June 30, 2019 includes the dilutive effect of stock options, RSUs, PSUs, and shares to be purchased under the ESPP and the Notes due 2023 . Certain common stock issuable under stock options, RSUs and PSUs 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 and Notes due 2025 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 and Notes due 2025 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 $20.50 per share and $81.54 per share for the Notes due 2024 and Notes due 2025

RELATED PARTY

RELATED PARTY	6 Months Ended
	Jun. 30, 2020
Related Party Transactions [Abstract]
RELATED PARTY	RELATED PARTY 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 June 30, 2020 and December 31, 2019 , $5.0 million aggregate principal amount of the Notes due 2023 were outstanding. See Note 8 . “Debt” for additional information related to this purchase.

DESCRIPTION OF BUSINESS AND B_2

DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION Policy (Policies)	6 Months Ended
	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation The accompanying condensed consolidated financial statements are presented in accordance with accounting principles generally accepted in the United States (“U.S.”), or GAAP. The condensed 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	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, allowance for doubtful accounts, stock-based compensation, inventory valuation, accrued warranty obligations, fair value of debt derivatives, fair value of acquired intangible assets and goodwill, useful lives of acquired intangible assets and property and equipment, incremental borrowing rate for right-of-use assets and lease liability, legal contingencies, 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. The worldwide spread of the COVID-19 virus has resulted in a global slowdown of economic activity which decreased demand for a broad variety of goods and services, including from our customers, while also disrupting sales channels and marketing activities for an unknown period of time and may continue to create significant uncertainty in future operational and financial performance. The Company expects this to result in negative impact on its sales and its results of operations. In preparing the Company’s condensed consolidated financial statements in accordance with GAAP, the Company is required to make estimates, assumptions and judgments that affect the amounts reported in its financial statements and the accompanying disclosures. Estimates and assumptions about future events and their effects cannot be determined with certainty and therefore require the exercise of judgment. As of the date of issuance of these financial statements, the Company is not aware of any specific event or circumstance that would require the Company to update its estimates, judgments or revise the carrying value of its assets or liabilities. These estimates may change, as new events occur and additional information is obtained, and are recognized in the condensed consolidated financial statements as soon as they become known. Actual results could differ from those estimates and any such differences may be material to the Company’s financial statements.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements 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. The Company adopted the new standard effective January 1, 2020 on a prospective basis and the adoption of this guidance did not have a material impact on its 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 current expected credit loss (CECL) model which will result in earlier recognition of credit losses. On January 1, 2020, the Company on a prospective basis adopted Topic 326, the measurement of expected credit losses under the CECL model is applicable to financial assets measured at amortized cost, including accounts receivable. The adoption of this guidance did not have a material impact on the Company’s consolidated financial statements.
Fair Value Measurement	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.
Earnings 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 , Warrants issued in conjunction with the Notes due 2024 , and from May 20, 2020 to the end of the reporting period, the Notes due 2025 and Warrants issued in conjunction with the Notes due 2025 . See Note 8. “Debt” for additional information. 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, Notes due 2024 , warrants issued in conjunction with the Notes due 2024 , Notes due 2025 , warrants issued in conjunction with the Notes due 2025 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.

REVENUE RECOGNITION (Tables)

REVENUE RECOGNITION (Tables)	6 Months Ended
	Jun. 30, 2020
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: Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Primary geographical markets: United States $ 100,791 $ 99,909 $ 280,391 $ 177,595 International 24,747 34,185 50,692 56,649 Total $ 125,538 $ 134,094 $ 331,083 $ 234,244 Timing of revenue recognition: Products delivered at a point in time $ 114,299 $ 124,336 $ 308,978 $ 214,736 Products and services delivered over time 11,239 9,758 22,105 19,508 Total $ 125,538 $ 134,094 $ 331,083 $ 234,244
Summary of Contract Assets and Contract Liabilities, and Changes in Balances from Contracts with Customers	Significant changes in the balances of contract liabilities (deferred revenues) during the period are as follows (in thousands): Contract Liabilities Balance on December 31, 2019 $ 181,987 Revenue recognized (66,841 ) Increase due to billings 36,087 Balance as of June 30, 2020 $ 151,233 Receivables, and contract assets and contract liabilities from contracts with customers are as follows: June 30, December 31, (In thousands) Receivables $ 89,504 $ 145,413 Short-term contract assets (Prepaid expenses and other assets) 16,416 15,055 Long-term contract assets (Other assets) 46,960 42,087 Short-term contract liabilities (Deferred revenues) 40,256 81,783 Long-term contract liabilities (Deferred revenues) 110,977 100,204 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, 2019 $ 57,142 Amount recognized (8,439 ) Increase 14,673 Balance as of June 30, 2020 $ 63,376
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: June 30, (In thousands) Fiscal year: 2020 (remaining six months) $ 21,679 2021 36,389 2022 31,357 2023 25,564 2024 20,373 Thereafter 15,871 Total $ 151,233

OTHER FINANCIAL INFORMATION (Ta

OTHER FINANCIAL INFORMATION (Tables)	6 Months Ended
	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Accounts Receivable, Net	Accounts receivable, net consist of the following: June 30, December 31, (In thousands) Accounts receivable $ 89,800 $ 145,977 Allowance for doubtful accounts (296 ) (564 ) Accounts receivable, net $ 89,504 $ 145,413
Schedule of Allowance for Doubtful Accounts	The following table sets forth activities in the allowance for doubtful accounts for the periods indicated. Three Months Ended Six Months Ended 2020 (In thousands) Balance, at beginning of the period $ 374 $ 564 Net charges to expenses 81 185 Write-offs, net of recoveries (159 ) (453 ) Balance, at end of the period $ 296 $ 296
Schedule of Inventory	Inventory consist of the following: June 30, December 31, (In thousands) Raw materials $ 5,800 $ 4,197 Finished goods 25,386 27,859 Total inventory $ 31,186 $ 32,056
Schedule of Accrued Liabilities	Accrued liabilities consist of the following: June 30, December 31, (In thousands) Salaries, commissions, incentive compensation and benefits $ 3,607 $ 5,524 Customer rebates and sales incentives 20,741 24,198 Freight 2,640 4,908 Operating lease liabilities, current 3,570 3,170 Other 16,133 9,292 Total accrued liabilities $ 46,691 $ 47,092

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS (Tables)	6 Months Ended
	Jun. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill and Intangible Assets	The Company’s goodwill and purchased intangible assets as of June 30, 2020 and December 31, 2019 are as follows: June 30, 2020 December 31, 2019 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: Developed technology 13,100 (4,185 ) 8,915 13,100 (3,093 ) 10,007 Customer relationships 23,100 (4,215 ) 18,885 23,100 (2,814 ) 20,286 Total purchased intangible assets $ 36,486 $ (8,400 ) $ 28,086 $ 36,486 $ (5,907 ) $ 30,579
Schedule of Amortization Expense	Amortization expense related to finite-lived intangible assets are as follows: Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Developed technology, and patents and licensed technology $ 546 $ 546 $ 1,092 $ 1,092 Customer relationships 700 635 1,401 1,271 Total amortization expense $ 1,246 $ 1,181 $ 2,493 $ 2,363

WARRANTY OBLIGATIONS (Tables)

WARRANTY OBLIGATIONS (Tables)	6 Months Ended
	Jun. 30, 2020
Product Warranties Disclosures [Abstract]
Summary of Warranty Activities	The Company’s warranty activities were as follows: Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Warranty obligations, beginning of period $ 37,501 $ 31,042 $ 37,098 $ 31,294 Accruals for warranties issued during period 766 1,312 2,290 2,170 Changes in estimates 1,748 699 3,425 1,503 Settlements (2,578 ) (2,206 ) (5,848 ) (4,502 ) Increase due to accretion expense 804 550 1,578 1,101 Other (334 ) 1,597 (636 ) 1,428 Warranty obligations, end of period 37,907 32,994 37,907 32,994 Less: current portion (10,170 ) (7,468 ) (10,170 ) (7,468 ) Noncurrent $ 27,737 $ 25,526 $ 27,737 $ 25,526

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Schedule of Liabilities Measured at Fair Value on a Recurring Basis	The following table presents the Company’s warranty obligation that were measured at fair value on a recurring basis and its categorization within the fair value hierarchy. June 30, December 31, 2019 (In thousands) Level 3 Level 3 Liabilities: Warranty obligations Current $ 6,917 $ 6,794 Non-current 14,215 13,012 Total warranty obligations measured at fair value 21,132 19,806 Total liabilities measured at fair value $ 21,132 $ 19,806 The following table presents the fair value and the change in fair value for the Convertible notes hedge asset and Warrants liability: Convertible notes hedge Warrants liability (In thousands) Fair value as of March 9, 2020 $ 89,056 $ 71,552 Change in the fair value (41,171 ) (32,915 ) Fair value as of March 31, 2020 47,885 38,637 Change in the fair value 69,223 57,715 Fair value as of May 20, 2020 $ 117,108 $ 96,352
Schedule of Changes in Nonfinancial Liabilities Related to Warrant Obligations Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs	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. Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Balance at beginning of period $ 20,425 $ 12,065 $ 19,806 $ 11,757 Accruals for warranties issued during period 766 1,312 2,290 2,170 Changes in estimates 983 519 1,598 860 Settlements (1,511 ) (1,188 ) (3,504 ) (2,460 ) Increase due to accretion expense 804 550 1,578 1,101 Other (335 ) 1,598 (636 ) 1,428 Balance at end of period $ 21,132 $ 14,856 $ 21,132 $ 14,856
Summary of Significant Unobservable Inputs used in the Fair Value Measurement of Liabilities Designated as Level 3	As of June 30, 2020 and December 31, 2019 , 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 June 30, December 31, Warranty obligations for microinverters sold since January 1, 2014 Discounted cash flows Profit element and risk premium 15% 14% Credit-adjusted risk-free rate 16% 16%

RESTRUCTURING (Tables)

RESTRUCTURING (Tables)	6 Months Ended
	Jun. 30, 2020
Restructuring and Related Activities [Abstract]
Restructuring and Related Costs	Restructuring expense consist of the following: Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Redundancy and employee severance and benefit arrangements $ — $ 631 $ — $ 1,099 Lease loss reserves — — — (100 ) Total restructuring charges $ — $ 631 $ — $ 999

DEBT (Tables)

DEBT (Tables)	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
Schedule of Derivative Instruments	The following table presents the fair value and the change in fair value for the convertible note embedded derivative (in thousands): Convertible note embedded derivative (In thousands) Fair value as of March 9, 2020 $ 68,700 Change in the fair value (23,600 ) Fair value as of March 31, 2020 45,100 Change in the fair value 71,200 Fair value as of May 20, 2020 $ 116,300
Schedule of Debt	The following table provides information regarding the Company’s long-term debt. June 30, December 31, (In thousands) Convertible notes Notes due 2025 $ 320,000 $ — Less: unamortized discount and issuance costs (72,000 ) — Carrying amount of Notes due 2025 248,000 — Notes due 2024 132,000 132,000 Less: unamortized discount and issuance costs (32,301 ) (35,815 ) Carrying amount of Notes due 2024 99,699 96,185 Notes due 2023 5,000 5,000 Less: unamortized issuance costs (122 ) (143 ) Carrying amount of Notes due 2023 4,878 4,857 Sale of long-term financing receivable recorded as debt 2,868 4,501 Total carrying amount of debt 355,445 105,543 Less: current portion of convertible notes and long-term financing receivable recorded as debt (102,271 ) (2,884 ) Long-term debt $ 253,174 $ 102,659 The following table presents the total amount of interest cost recognized relating to the Notes due 2025 : Three Months Ended Six Months Ended (In thousands) Contractual interest expense $ 200 $ 249 Amortization of debt discount 3,069 3,812 Amortization of debt issuance costs 381 468 Total interest cost recognized $ 3,650 $ 4,529 The following table presents the total amount of interest cost recognized relating to the Notes due 2024 : Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Contractual interest expense $ 330 $ 92 $ 660 $ 92 Amortization of debt discount 1,621 416 3,183 416 Amortization of debt issuance costs 166 45 332 45 Total interest cost recognized $ 2,117 $ 553 $ 4,175 $ 553 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 . Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Contractual interest expense $ 50 $ 483 $ 100 $ 1,133 Amortization of debt issuance costs 10 96 20 225 Total interest costs recognized $ 60 $ 579 $ 120 $ 1,358
Schedule of Fair Value Of Convertible Notes Hedge and Warrants Liability	The following table presents the Company’s warranty obligation that were measured at fair value on a recurring basis and its categorization within the fair value hierarchy. June 30, December 31, 2019 (In thousands) Level 3 Level 3 Liabilities: Warranty obligations Current $ 6,917 $ 6,794 Non-current 14,215 13,012 Total warranty obligations measured at fair value 21,132 19,806 Total liabilities measured at fair value $ 21,132 $ 19,806 The following table presents the fair value and the change in fair value for the Convertible notes hedge asset and Warrants liability: Convertible notes hedge Warrants liability (In thousands) Fair value as of March 9, 2020 $ 89,056 $ 71,552 Change in the fair value (41,171 ) (32,915 ) Fair value as of March 31, 2020 47,885 38,637 Change in the fair value 69,223 57,715 Fair value as of May 20, 2020 $ 117,108 $ 96,352

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	6 Months Ended
	Jun. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Components of Lease	The components of lease expense are presented as follows: Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Operating lease costs $ 1,280 $ 564 $ 2,502 $ 1,063 The components of lease liabilities are presented as follows: June 30, December 31, (In thousands) Operating lease liabilities, current (Accrued liabilities) $ 3,570 $ 3,170 Operating lease liabilities, noncurrent (Other liabilities) 10,202 9,542 Total operating lease liabilities $ 13,772 $ 12,712 Supplemental lease information: Weighted average remaining lease term 5.4 years 5.5 years Weighted average discount rate 8.3% 8.6% Supplemental cash flow and other information related to operating leases, are as follows: Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 1,145 $ 857 $ 2,159 $ 1,594 Non-cash investing activities: Lease liabilities arising from obtaining right-of-use assets $ — $ 4,834 $ 2,941 $ 4,834
Schedule of Future Minimum Rental Payments for Operating Leases	Undiscounted cash flows of operating lease liabilities as of June 30, 2020 are as follows: Lease Amounts (In thousands) Year: 2020 (remaining six months) $ 2,307 2021 4,679 2022 3,365 2023 2,648 2024 1,445 2025 and thereafter 1,949 Total lease payments 16,393 Less: imputed lease interest (2,621 ) Total lease liabilities $ 13,772

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	6 Months Ended
	Jun. 30, 2020
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 condensed consolidated statements of operations for the periods presented. Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Cost of revenues $ 1,337 $ 386 $ 1,943 $ 617 Research and development 3,263 1,128 5,182 1,844 Sales and marketing 3,610 1,360 5,552 2,359 General and administrative 4,090 1,729 7,138 3,017 Restructuring — 332 — 387 Total $ 12,300 $ 4,935 $ 19,815 $ 8,224
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. Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Stock options, RSUs, and PSUs $ 11,557 $ 4,760 $ 18,634 $ 7,982 Employee stock purchase plan 743 175 1,181 242 Total $ 12,300 $ 4,935 $ 19,815 $ 8,224
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	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. Three Months Ended Six Months Ended 2020 2019 2020 2019 Weighted average grant date fair value $ 38.45 $ 9.16 $ 38.45 $ 9.16 Expected term (in years) 3.8 3.8 3.8 3.8 Expected volatility 86.4 % 89.1 % 86.4 % 89.1 % Annual risk-free rate of return 0.1 % 2.1 % 0.1 % 2.1 % Dividend yield — % — % — % — %
Share-based Compensation, Performance Shares Award Outstanding Activity	The following is a summary of PSU activity. Number of Weighted- Weighted- Aggregate (1) (In thousands) (Years) (In thousands) Outstanding at December 31, 2019 955 $ 9.83 Granted 974 30.45 Vested (1,450 ) 10.20 $ 52,144 Canceled — — Outstanding at June 30, 2020 479 $ 50.37 0.7 $ 22,777 (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 June 30, 2020 is based on the closing price of the Company’s stock on June 30, 2020 or the earlier of the last trading day prior to June 30, 2020 , if June 30, 2020 is a non-trading day. The Company’s stock fair value used in this computation was $47.57 per share.
Summary of Stock Option Activity	The following is a summary of stock option activity. Number of Weighted- Weighted- Aggregate (1) (In thousands) (Years) (In thousands) Outstanding at December 31, 2019 4,097 $ 2.18 Granted 11 64.17 Exercised (968 ) 2.08 $ 50,611 Canceled (75 ) 7.34 Outstanding at June 30, 2020 3,065 $ 2.30 4.0 $ 138,877 Vested and expected to vest at June 30, 2020 3,065 $ 2.30 3.0 $ 138,877 Exercisable at June 30, 2020 2,270 $ 2.37 3.9 $ 102,649 (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 June 30, 2020 is based on the closing price of the Company’s stock fair value on June 30, 2020 or the earlier of the last trading day prior to June 30, 2020 , if June 30, 2020 is a non-trading day. The Company’s stock fair value used in this computation was $47.57 per share.
Summary of Stock Option Outstanding	The following table summarizes information about stock options outstanding at June 30, 2020 . Options Outstanding Options Exercisable Range of Exercise Prices Number of Weighted- Weighted- Number of Weighted- (In thousands) (Years) (In thousands) $0.70 —– $1.11 706 4.6 $ 0.82 546 $ 0.80 $1.29 —– $1.29 1,000 4.2 1.29 687 1.29 $1.31 —– $1.31 709 3.8 1.31 500 1.31 $1.37 —– $14.58 639 3.2 5.60 536 6.22 $64.17 —– $64.17 11 6.9 64.17 1 64.17 Total 3,065 4.0 $ 2.30 2,270 $ 2.37
Summary of Restricted Stock Unit Activity	The following is a summary of RSU activity. Number of Weighted- Weighted- Aggregate (1) (In thousands) (Years) (In thousands) Outstanding at December 31, 2019 4,263 $ 7.19 Granted 1,077 36.62 Vested (1,380 ) 6.60 $ 55,925 Canceled (66 ) 16.15 Outstanding at June 30, 2020 3,894 $ 15.39 1.24 $ 185,236 Expected to vest at June 30, 2020 3,894 $ 15.39 1.24 $ 185,236 (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 June 30, 2020 is based on the closing price of the Company’s stock on June 30, 2020 or the earlier of the last trading day prior to June 30, 2020 , if June 30, 2020 is a non-trading day. The Company’s stock fair value used in this computation was $47.57 per share.

NET INCOME (LOSS) PER SHARE (Ta

NET INCOME (LOSS) PER SHARE (Tables)	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Schedule of Computation of Basic and 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. Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands, except per share data) Numerator: Net income (loss) $ (47,294 ) $ 10,618 $ 21,642 $ 13,383 Notes due 2023 interest and financing costs, net — 430 89 1,006 Adjusted net income (loss) $ (47,294 ) $ 11,048 $ 21,731 $ 14,389 Denominator: Shares used in basic per share amounts: Weighted average common shares outstanding 125,603 113,677 124,567 110,951 Shares used in diluted per share amounts: Weighted average common shares outstanding 125,603 113,677 124,567 110,951 Effect of dilutive securities: Employee stock-based awards — 8,326 7,449 8,240 Warrants (issued in conjunction with Notes due 2024) — — 2,641 — Notes due 2024 — — 3,353 — Notes due 2023 — 8,734 900 10,209 Weighted average common shares outstanding for diluted calculation 125,603 130,737 138,910 129,400 Basic and diluted net income (loss) per share Net income (loss) per share, basic $ (0.38 ) $ 0.09 $ 0.17 $ 0.12 Net income per share, diluted $ (0.38 ) $ 0.08 $ 0.16 $ 0.11
Schedule of Potentially Dilutive Securities Excluded from the Computation of Diluted Net Loss Per Share	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. Three Months Ended Six Months Ended 2020 2019 2020 2019 (In thousands) Employee stock-based awards 6,459 66 294 77 Warrants (issued in conjunction with Notes due 2024) 3,039 — — — Notes due 2024 3,677 — — — Warrants (issued in conjunction with Notes due 2025) 3,924 — 3,430 — Notes due 2025 2,771 — 2,031 — Notes due 2023 900 — — — Total 20,770 66 5,755 77

REVENUE RECOGNITION - Summary o

REVENUE RECOGNITION - Summary of Disaggregated Revenue by Primary Geographical Market and Timing of Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues	$ 125,538	$ 134,094	$ 331,083	$ 234,244
Products delivered at a point in time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues	114,299	124,336	308,978	214,736
Products and services delivered over time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues	11,239	9,758	22,105	19,508
United States
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues	100,791	99,909	280,391	177,595
International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues	$ 24,747	$ 34,185	$ 50,692	$ 56,649

REVENUE RECOGNITION - Summary_2

REVENUE RECOGNITION - Summary of Contract Assets and Contract Liabilities from Contracts with Customers (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Receivables	$ 89,504	$ 145,413
Short-term contract assets (Prepaid expenses and other assets)	16,416	15,055
Long-term contract assets (Other assets)	46,960	42,087
Short-term contract liabilities (Deferred revenues)	40,256	81,783
Long-term contract liabilities (Deferred revenues)	$ 110,977	$ 100,204

REVENUE RECOGNITION - Narrative

REVENUE RECOGNITION - Narrative (Details) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Revenue from Contract with Customer [Abstract]
Contract asset impairment charges	$ 0	$ 0

REVENUE RECOGNITION - Summary_3

REVENUE RECOGNITION - Summary of Significant Changes in the Balances of Contract Liabilities and Assets (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2020USD ($)
Contract Assets
Balance, beginning of period	$ 57,142
Revenue recognized	(8,439)
Increase	14,673
Balance, end of period	63,376
Contract Liabilities
Balance, beginning of period	181,987
Revenue recognized	(66,841)
Increase due to billings	36,087
Balance, end of period	$ 151,233

REVENUE RECOGNITION - Summary_4

REVENUE RECOGNITION - Summary of Estimated Revenue Expected to be Recognized in Future Periods (Details) $ in Thousands	Jun. 30, 2020USD ($)
Revenue from Contract with Customer [Abstract]
Total estimated revenue expected to be recognized in future periods	$ 151,233
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-07-01
Revenue from Contract with Customer [Abstract]
Total estimated revenue expected to be recognized in future periods	$ 21,679
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total estimated revenue expected to be recognized in future periods, expected timing	6 months
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	$ 36,389
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	$ 31,357
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	$ 25,564
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	$ 20,373
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	$ 15,871
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total estimated revenue expected to be recognized in future periods, expected timing

OTHER FINANCIAL INFORMATION - A

OTHER FINANCIAL INFORMATION - Accounts Receivable (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accounts receivable	$ 89,800	$ 145,977
Allowance for doubtful accounts	(296)	(564)
Accounts receivable, net	$ 89,504	$ 145,413

OTHER FINANCIAL INFORMATION -_2

OTHER FINANCIAL INFORMATION - Accounts Receivable, Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance, at beginning of year	$ 374	$ 564
Provision for doubtful accounts	81	185	$ 207
Write-offs, net of recoveries	(159)	(453)
Balance, at end of year	$ 296	$ 296

OTHER FINANCIAL INFORMATION - I

OTHER FINANCIAL INFORMATION - Inventory (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Raw materials	$ 5,800	$ 4,197
Finished goods	25,386	27,859
Total inventory	$ 31,186	$ 32,056

OTHER FINANCIAL INFORMATION -_3

OTHER FINANCIAL INFORMATION - Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Salaries, commissions, incentive compensation and benefits	$ 3,607	$ 5,524
Customer rebates and sales incentives	20,741	24,198
Freight	2,640	4,908
Operating lease liabilities, current	3,570	3,170
Other	16,133	9,292
Total accrued liabilities	$ 46,691	$ 47,092

GOODWILL AND INTANGIBLE ASSET_2

GOODWILL AND INTANGIBLE ASSETS - Schedule of Goodwill and Intangible Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
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	36,486
Accumulated Amortization	(8,400)	(5,907)
Net	28,086	30,579
Developed technology
Intangible assets with finite lives:
Gross	13,100	13,100
Accumulated Amortization	(4,185)	(3,093)
Net	8,915	10,007
Customer relationship
Intangible assets with finite lives:
Gross	23,100	23,100
Accumulated Amortization	(4,215)	(2,814)
Net	$ 18,885	$ 20,286

GOODWILL AND INTANGIBLE ASSET_3

GOODWILL AND INTANGIBLE ASSETS - Amortization Expense (Details) - USD ($) $ in Thousands	Aug. 09, 2018	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets		$ 1,246	$ 1,181	$ 2,493	$ 2,363
Developed technology, and patents and licensed technology
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets		546	546	1,092	1,092
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets		$ 700	$ 635	$ 1,401	$ 1,271
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

WARRANTY OBLIGATIONS - Summary

WARRANTY OBLIGATIONS - Summary of Warranty Activities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Changes in the Company's product warranty liability
Warranty obligations, beginning of period	$ 37,501	$ 31,042	$ 37,098	$ 31,294
Accruals for warranties issued during period	766	1,312	2,290	2,170
Changes in estimates	1,748	699	3,425	1,503
Settlements	(2,578)	(2,206)	(5,848)	(4,502)
Increase due to accretion expense	804	550	1,578	1,101
Other	(334)	1,597	(636)	1,428
Warranty obligations, end of period	37,907	32,994	37,907	32,994
Less: current portion	(10,170)	(7,468)	(10,170)	(7,468)	$ (10,078)
Noncurrent	$ 27,737	$ 25,526	$ 27,737	$ 25,526	$ 27,020

WARRANTY OBLIGATIONS - Narrativ

WARRANTY OBLIGATIONS - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Product Warranties Disclosures [Abstract]
Additional warranty expense	$ 1,748	$ 699	$ 3,425	$ 1,503

FAIR VALUE MEASUREMENTS - Narra

FAIR VALUE MEASUREMENTS - Narrative (Details) - USD ($)	6 Months Ended
	Jun. 30, 2020	May 20, 2020	Mar. 31, 2020	Mar. 09, 2020	Jun. 05, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrants obligations measured at fair value		$ 96,400,000
Increase in liability as a result of increasing the profit element and risk premium input by 100 basis points	$ 200,000
Decrease in liability as a result of decreasing the profit element and risk premium input by 100 basis points	200,000
Decrease in liability as a result of increasing the discount rate by 100 basis points	900,000
Increase in liability as a result of decreasing the discount rate by 100 basis points	1,000,000
Convertible Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible notes embedded derivative		117,100,000
Convertible Notes | Convertible Senior Notes Due 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument face amount				$ 320,000,000
Interest rate				0.25%
Convertible notes embedded derivative		116,300,000	$ 45,100,000	$ 68,700,000
Warrants obligations measured at fair value		$ 96,352,000	$ 38,637,000	$ 71,552,000
Convertible Notes | Convertible Senior Notes Due 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument face amount					$ 132,000,000
Interest rate					1.00%
Level 1 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	598,500,000
Level 2 | Recurring | Convertible Notes | Convertible Senior Notes Due 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes payable fair value	288,900,000
Level 2 | Recurring | Convertible Notes | Convertible Senior Notes Due 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes payable fair value	$ 350,500,000

FAIR VALUE MEASUREMENTS - Sched

FAIR VALUE MEASUREMENTS - Schedule of Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Liabilities:
Warranty obligations, current	$ 10,170		$ 10,078	$ 7,468
Warranty obligations, non-current	27,737		27,020	25,526
Total warranty obligations measured at fair value	37,907	$ 37,501	37,098	$ 32,994	$ 31,042	$ 31,294
Recurring | Level 3
Liabilities:
Warranty obligations, current	6,917		6,794
Warranty obligations, non-current	14,215		13,012
Total warranty obligations measured at fair value	21,132		19,806
Total liabilities measured at fair value	$ 21,132		$ 19,806

FAIR VALUE MEASUREMENTS - Sch_2

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	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 20,425	$ 12,065	$ 19,806	$ 11,757
Accruals for warranties issued during period	766	1,312	2,290	2,170
Changes in estimates	983	519	1,598	860
Settlements	(1,511)	(1,188)	(3,504)	(2,460)
Increase due to accretion expense	804	550	1,578	1,101
Other	(335)	1,598	(636)	1,428
Balance at end of period	$ 21,132	$ 14,856	$ 21,132	$ 14,856

FAIR VALUE MEASUREMENTS - Summa

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	Jun. 30, 2020	Dec. 31, 2019
Profit element and risk premium
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warranty obligations, measurement input	0.15	0.14
Credit-adjusted risk-free rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warranty obligations, measurement input	0.16	0.16

RESTRUCTURING - Summary of Rest

RESTRUCTURING - Summary of Restructuring Charges (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 0	$ 631	$ 0	$ 999
Redundancy and employee severance and benefit arrangements
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0	631	0	1,099
Lease loss reserves
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, accrual adjustment	$ 0	$ 0	$ 0	$ (100)

DEBT - Long-term debt (Details)

DEBT - Long-term debt (Details) - USD ($) $ in Thousands	Jun. 30, 2020	May 20, 2020	Mar. 31, 2020	Mar. 09, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Total carrying amount of debt	$ 355,445				$ 105,543
Less: current portion of convertible notes and long-term financing receivable recorded as debt	(102,271)				(2,884)
Long-term debt	253,174				102,659
Convertible Notes
Debt Instrument [Line Items]
Convertible notes embedded derivative		$ 117,100
Convertible Notes | Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Long-term debt, gross	320,000				0
Less unamortized discount and issuance costs	(72,000)				0
Total carrying amount of debt	248,000				0
Convertible notes embedded derivative		$ 116,300	$ 45,100	$ 68,700
Convertible Notes | Convertible Senior Notes Due 2024
Debt Instrument [Line Items]
Long-term debt, gross	132,000				132,000
Less unamortized discount and issuance costs	(32,301)				(35,815)
Total carrying amount of debt	99,699				96,185
Convertible Notes | Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Long-term debt, gross	5,000				5,000
Less unamortized discount and issuance costs	(122)				(143)
Total carrying amount of debt	4,878				4,857
Financing Receivable | Financing Receivable Recorded as Debt
Debt Instrument [Line Items]
Long-term debt, gross	$ 2,868				$ 4,501

DEBT - Convertible Senior Notes

DEBT - Convertible Senior Notes due in 2025 Narrative (Details)	Mar. 09, 2020USD ($)trading_day$ / sharesshares	Jun. 05, 2019USD ($)	Jun. 30, 2020USD ($)$ / sharesshares	Jun. 30, 2019USD ($)	May 20, 2020USD ($)$ / sharesshares	May 19, 2020shares	Mar. 31, 2020USD ($)	Dec. 31, 2019$ / sharesshares
Debt Instrument [Line Items]
Common stock, par value (in usd per share) | $ / shares			$ 0.00001		$ 0.00001			$ 0.00001
Common stock, shares authorized (in shares) | shares			200,000,000		200,000,000	150,000,000		150,000,000
Payment for bonds hedge			$ 89,056,000	$ 36,313,000
Proceeds from sale of warrants		$ 29,800,000	$ 71,552,000	$ 29,819,000
Warrants obligations measured at fair value					$ 96,400,000
Convertible Notes
Debt Instrument [Line Items]
Convertible notes embedded derivative					117,100,000
Convertible Notes | Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Debt instrument face amount	$ 320,000,000
Interest rate	0.25%
Conversion ratio	0.0122637
Debt conversion price (in USD per share) | $ / shares	$ 81.54
Proceeds from convertible debt	$ 313,000,000
Convertible notes embedded derivative	68,700,000				116,300,000		$ 45,100,000
Embedded derivative, host contract	251,300,000
Debt issuance costs	$ 7,600,000
Effective percentage rate			5.18%
Unamortized discount			$ 64,900,000
Remaining discount amortization period			4 years 8 months 12 days
Conversion shares (in shares) | shares	3,900,000
Payment for bonds hedge	$ 89,100,000
Warrants issued, strike price (in USD per share) | $ / shares	$ 106.94
Proceeds from sale of warrants	$ 71,600,000
Warrants obligations measured at fair value	$ 71,552,000				$ 96,352,000		$ 38,637,000
Period One | Convertible Notes | Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Number of threshold trading days | trading_day	20
Number of consecutive trading days | trading_day	30
Threshold percentage	130.00%
Period Two | Convertible Notes | Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Number of consecutive trading days | trading_day	5
Threshold percentage	100.00%
Measurement period percentage of stock price trigger	98.00%

DEBT - Schedule of Convertible

DEBT - Schedule of Convertible Senior Notes due in 2025 (Details) - Convertible Notes - Convertible Senior Notes Due 2025 - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Debt Instrument [Line Items]
Contractual interest expense	$ 200	$ 249
Amortization of debt discount	3,069	3,812
Amortization of debt issuance costs	381	468
Total interest cost recognized	$ 3,650	$ 4,529

DEBT - Convertible Note Embedde

DEBT - Convertible Note Embedded Derivative (Details) - Convertible Notes - USD ($) $ in Thousands	1 Months Ended	2 Months Ended
	Mar. 31, 2020	May 20, 2020
Debt Instrument [Line Items]
Embedded derivative, ending balance		$ 117,100
Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Embedded derivative, beginning balance	$ 68,700	45,100
Embedded derivative, change in the fair value	(23,600)	71,200
Embedded derivative, ending balance	$ 45,100	$ 116,300

DEBT - Convertible Notes Hedge

DEBT - Convertible Notes Hedge and Warrant Liability (Details) - USD ($) $ in Thousands	1 Months Ended	2 Months Ended	3 Months Ended		6 Months Ended
	Mar. 31, 2020	May 20, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Debt Instrument [Line Items]
Convertible notes hedge, change in the fair value			$ (59,692)	$ 0	$ (44,348)	$ 0
Warrants liability, ending balance		$ 96,400
Convertible Notes | Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Convertible notes hedge, beginning balance	$ 89,056	47,885	47,885
Convertible notes hedge, change in the fair value	(41,171)	69,223
Convertible notes hedge, ending balance	47,885	117,108
Warrants liability, beginning balance	71,552	38,637	$ 38,637
Warrants liability, change in fair value	(32,915)	57,715
Warrants liability, ending balance	$ 38,637	$ 96,352

DEBT - Convertible Senior Not_2

DEBT - Convertible Senior Notes due 2024 Narrative (Details) $ / shares in Units, shares in Millions	Mar. 09, 2020trading_day	Jun. 05, 2019USD ($)trading_day$ / sharesshares	Jun. 30, 2020USD ($)trading_day$ / shares	Jun. 30, 2019USD ($)	Dec. 31, 2019USD ($)
Debt Instrument [Line Items]
Debt, current			$ 355,445,000		$ 105,543,000
Deferred tax assets, net			93,872,000		74,531,000
Payment for bonds hedge			89,056,000	$ 36,313,000
Proceeds from sale of warrants		$ 29,800,000	71,552,000	$ 29,819,000
Convertible Notes | Convertible Senior Notes Due 2024
Debt Instrument [Line Items]
Debt instrument face amount		$ 132,000,000
Interest rate		1.00%
Debt conversion price (in USD per share) | $ / shares		$ 20.5010
Proceeds from convertible debt		$ 128,000,000
Conversion ratio		0.0487781
Debt, current			$ 99,699,000		96,185,000
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	$ 2,600,000		2,900,000
Debt issuance costs, allocated to capital		$ 1,300,000
Unamortized discount			$ 29,700,000		$ 32,900,000
Remaining discount amortization period			3 years 10 months 24 days
Conversion shares (in shares) | shares		6.4
Payment for bonds hedge		$ 36,300,000
Warrants sold (in shares) | shares		6.4
Warrants issued, strike price (in USD per share) | $ / shares		$ 25.2320
Period One | Convertible Notes | Convertible Senior Notes 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 Notes Due 2024
Debt Instrument [Line Items]
Number of consecutive trading days | trading_day	5
Threshold percentage		100.00%

DEBT - Schedule of Convertibl_2

DEBT - Schedule of Convertible Senior Notes due 2024 (Details) - Convertible Notes - Convertible Senior Notes Due 2024 - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Debt Instrument [Line Items]
Contractual interest expense	$ 330	$ 92	$ 660	$ 92
Amortization of debt discount	1,621	416	3,183	416
Amortization of debt issuance costs	166	45	332	45
Total interest cost recognized	$ 2,117	$ 553	$ 4,175	$ 553

DEBT - Convertible Senior Not_3

DEBT - Convertible Senior Notes due 2023 Narrative (Details) - Convertible Senior Notes Due 2023	Jun. 05, 2019USD ($)shares	Aug. 31, 2018USD ($)$ / shares	Jun. 30, 2020USD ($)	Dec. 31, 2019USD ($)
Debt Instrument [Line Items]
Conversion shares (in shares) | shares	10,801,080
Fees paid for repurchase and exchange of convertible notes	$ 6,000,000
Convertible Notes
Debt Instrument [Line Items]
Debt instrument face amount		$ 65,000,000	$ 5,000,000	$ 5,000,000
Interest rate		4.00%
Debt converted	$ 60,000,000
Debt conversion price (in USD per share) | $ / shares		$ 5.56
Redemption price percentage		100.00%
Conversion ratio		0.180018

DEBT - Schedule of Convertibl_3

DEBT - Schedule of Convertible Senior Notes due 2023 (Details) - Convertible Notes - Convertible Senior Notes Due 2023 - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Debt Instrument [Line Items]
Contractual interest expense	$ 50	$ 483	$ 100	$ 1,133
Amortization of debt issuance costs	10	96	20	225
Total interest cost recognized	$ 60	$ 579	$ 120	$ 1,358

DEBT - Sale of Long - Term Fina

DEBT - Sale of Long - Term Financing Receivables (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018
Financing Receivable | Financing Receivable Recorded As Debt
Debt Instrument [Line Items]
Proceeds from debt, net of issuance costs	$ 2.8	$ 5.6

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Narrative (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Term of lease contract, maximum renewal term	12 years
Purchase obligation	$ 75,200,000
Line of Credit Facility [Line Items]
Letters of credit outstanding	0
Potential positive impact of approval of requested Tariff refunds	$ 39,000,000
Letter of credit
Line of Credit Facility [Line Items]
Line of credit		$ 44,700,000

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES - Lease Expense Components (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Operating lease costs	$ 1,280	$ 564	$ 2,502	$ 1,063

COMMITMENTS AND CONTINGENCIES_3

COMMITMENTS AND CONTINGENCIES - Lease Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Operating lease liabilities, current (Accrued liabilities)	$ 3,570	$ 3,170
Operating lease liabilities, noncurrent (Other liabilities)	10,202	9,542
Total operating lease liabilities	$ 13,772	$ 12,712
Weighted average remaining lease term	5 years 4 months 24 days	5 years 6 months
Weighted average discount rate	8.30%	8.60%

COMMITMENTS AND CONTINGENCIES_4

COMMITMENTS AND CONTINGENCIES - Supplemental Cash Flow and Other Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Operating cash flows from operating leases	$ 1,145	$ 857	$ 2,159	$ 1,594
Lease liabilities arising from obtaining right-of-use assets	$ 0	$ 4,834	$ 2,941	$ 4,834

COMMITMENTS AND CONTINGENCIES_5

COMMITMENTS AND CONTINGENCIES - Schedule of Minimum Lease Payments Under Noncancelable Operating Leases (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2020 (remaining six months)	$ 2,307
2021	4,679
2022	3,365
2023	2,648
2024	1,445
2025 and thereafter	1,949
Total lease payments	16,393
Less: imputed lease interest	(2,621)
Total lease liabilities	$ 13,772	$ 12,712

STOCK-BASED COMPENSATION - Summ

STOCK-BASED COMPENSATION - Summary of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 12,300	$ 4,935	$ 19,815	$ 8,224
Total unrecognized compensation cost	76,900		$ 76,900
Weighted-average recognition period for unrecognized compensation cost			2 years 1 month 6 days
Cost of revenues
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	1,337	386	$ 1,943	617
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	3,263	1,128	5,182	1,844
Sales and marketing
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	3,610	1,360	5,552	2,359
General and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	4,090	1,729	7,138	3,017
Restructuring
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 0	$ 332	$ 0	$ 387

STOCK-BASED COMPENSATION - Su_2

STOCK-BASED COMPENSATION - Summary of Stock-Based Compensation Expense Associated with Each Type of Award (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 12,300	$ 4,935	$ 19,815	$ 8,224
Stock options and RSUs and PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	11,557	4,760	18,634	7,982
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 743	$ 175	$ 1,181	$ 242

STOCK-BASED COMPENSATION - Su_3

STOCK-BASED COMPENSATION - Summary of the Weighted-Average Grant Date Fair Value of Options Granted (Details) - Stock options - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
The fair value of each option granted during the periods
Weighted average grant date fair value (in usd per share)	$ 38.45	$ 9.16	$ 38.45	$ 9.16
Expected term	3 years 9 months 18 days	3 years 9 months 18 days	3 years 9 months 18 days	3 years 9 months 18 days
Expected volatility	86.40%	89.10%	86.40%	89.10%
Annual risk-free rate of return	0.10%	2.10%	0.10%	2.10%
Dividend yield	0.00%	0.00%	0.00%	0.00%

STOCK-BASED COMPENSATION - Su_4

STOCK-BASED COMPENSATION - Summary of Stock Option Activity (Details) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended
	Jun. 30, 2020USD ($)$ / sharesshares
Number of Shares Outstanding
Outstanding, beginning balance (in shares) | shares	4,097
Granted (in shares) | shares	11
Exercised (in shares) | shares	(968)
Canceled (in shares) | shares	(75)
Outstanding, ending balance (in shares) | shares	3,065
Shares outstanding, vested and expected to vest (in shares) | shares	3,065
Shares outstanding, exercisable (in shares) | shares	2,270
Weighted- Average Exercise Price per Share
Outstanding, beginning balance (in usd per share)	$ 2.18
Granted (in usd per share)	64.17
Exercised (in usd per share)	2.08
Canceled (in usd per share)	7.34
Outstanding, ending balance (in usd per share)	2.30
Weighted-average exercise price, vested and expected (in usd per share)	2.30
Weighted-average exercise price, exercisable (in usd per share)	$ 2.37
Weighted-Average Remaining Contractual Term
Outstanding	4 years
Vested and expected to vest	3 years
Exercisable	3 years 10 months 24 days
Aggregate Intrinsic Value
Exercised | $	$ 50,611
Outstanding | $	138,877
Vested and expected to vest | $	138,877
Exercisable | $	$ 102,649
Share price (in usd per share)	$ 47.57

STOCK-BASED COMPENSATION - Su_5

STOCK-BASED COMPENSATION - Summary of Stock Options Outstanding (Details) shares in Thousands	6 Months Ended
	Jun. 30, 2020$ / sharesshares
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options outstanding, number of shares (shares) | shares	3,065
Options outstanding - weighted- average remaining life	4 years
Options outstanding - weighted- average exercise price (usd per share)	$ 2.30
Options exercisable - number of shares exercisable (shares) | shares	2,270
Options Exercisable - weighted-average exercise price (usd per share)	$ 2.37
$0.70 —– $1.11
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price range, lower limit (usd per share)	0.70
Exercise price range, upper limit (usd per share)	$ 1.11
Options outstanding, number of shares (shares) | shares	706
Options outstanding - weighted- average remaining life	4 years 7 months 6 days
Options outstanding - weighted- average exercise price (usd per share)	$ 0.82
Options exercisable - number of shares exercisable (shares) | shares	546
Options Exercisable - weighted-average exercise price (usd per share)	$ 0.80
$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 2 months 12 days
Options outstanding - weighted- average exercise price (usd per share)	$ 1.29
Options exercisable - number of shares exercisable (shares) | shares	687
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	709
Options outstanding - weighted- average remaining life	3 years 9 months 18 days
Options outstanding - weighted- average exercise price (usd per share)	$ 1.31
Options exercisable - number of shares exercisable (shares) | shares	500
Options Exercisable - weighted-average exercise price (usd per share)	$ 1.31
$1.37 —– $14.58
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)	$ 14.58
Options outstanding, number of shares (shares) | shares	639
Options outstanding - weighted- average remaining life	3 years 2 months 12 days
Options outstanding - weighted- average exercise price (usd per share)	$ 5.60
Options exercisable - number of shares exercisable (shares) | shares	536
Options Exercisable - weighted-average exercise price (usd per share)	$ 6.22
$64.17 —– $64.17
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price range, lower limit (usd per share)	64.17
Exercise price range, upper limit (usd per share)	$ 64.17
Options outstanding, number of shares (shares) | shares	11
Options outstanding - weighted- average remaining life	6 years 10 months 24 days
Options outstanding - weighted- average exercise price (usd per share)	$ 64.17
Options exercisable - number of shares exercisable (shares) | shares	1
Options Exercisable - weighted-average exercise price (usd per share)	$ 64.17

STOCK-BASED COMPENSATION - Su_6

STOCK-BASED COMPENSATION - Summary of Restricted Stock Unit Activity (Details) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended
	Jun. 30, 2020USD ($)$ / sharesshares
Aggregate Intrinsic Value
Share price (in usd per share)	$ 47.57
Restricted stock units
Number of Shares Outstanding
Outstanding, beginning balance (in shares) | shares	4,263
Granted (in shares) | shares	1,077
Vested (in shares) | shares	(1,380)
Canceled (in shares) | shares	(66)
Outstanding, ending balance (in shares) | shares	3,894
Number of shares outstanding, expected to vest (in shares) | shares	3,894
Weighted Average Fair Value per Share at Grant Date
Outstanding, beginning balance (in usd per share)	$ 7.19
Granted (in usd per share)	36.62
Vested (in usd per share)	6.60
Canceled (in usd per share)	16.15
Outstanding, ending balance (in usd per share)	15.39
Weighted-Average Fair Value per Share at Grant Date, Expected to vest (in usd per share)	$ 15.39
Weighted-Average Remaining Contractual Term
Weighted- Average Remaining Contractual Term	1 year 2 months 26 days
Expected to vest	1 year 2 months 26 days
Aggregate Intrinsic Value
Vested | $	$ 55,925
Outstanding | $	185,236
Aggregate intrinsic value, expected to vest | $	$ 185,236

STOCK-BASED COMPENSATION - Su_7

STOCK-BASED COMPENSATION - Summary of Performance Stock Unit Activity (Details) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended
	Jun. 30, 2020USD ($)$ / sharesshares
Aggregate Intrinsic Value
Share price (in usd per share)	$ 47.57
Performance shares
Number of Shares Outstanding
Outstanding, beginning balance (in shares) | shares	955
Granted (in shares) | shares	974
Vested (in shares) | shares	(1,450)
Canceled (in shares) | shares	0
Outstanding, ending balance (in shares) | shares	479
Weighted Average Fair Value per Share at Grant Date
Outstanding, beginning balance (in usd per share)	$ 9.83
Granted (in usd per share)	30.45
Vested (in usd per share)	10.20
Canceled (in usd per share)	0
Outstanding, ending balance (in usd per share)	$ 50.37
Weighted-Average Remaining Contractual Term
Weighted- Average Remaining Contractual Term	8 months 12 days
Aggregate Intrinsic Value
Vested | $	$ 52,144
Outstanding | $	$ 22,777

INCOME TAXES - Narrative (Detai

INCOME TAXES - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Tax Disclosure [Abstract]
Income taxes (benefit) provision	$ (6,561)	$ 591	$ (18,429)	$ 939
(Loss) income before income taxes	$ (53,855)	$ 11,209	$ 3,213	$ 14,322

NET INCOME (LOSS) PER SHARE - S

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		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator:
Net income (loss)	$ (47,294)	$ 10,618	$ 21,642	$ 13,383
Notes due 2023 interest and financing costs, net	0	430	89	1,006
Adjusted net income (loss)	$ (47,294)	$ 11,048	$ 21,731	$ 14,389
Denominator:
Weighted average common shares outstanding (in shares)	125,603	113,677	124,567	110,951
Employee stock-based awards (in shares)	0	8,326	7,449	8,240
Weighted average common shares outstanding for diluted calculation (in shares)	125,603	130,737	138,910	129,400
Net income (loss) per share, basic (in USD per share)	$ (0.38)	$ 0.09	$ 0.17	$ 0.12
Net income per share, diluted (in USD per share)	$ (0.38)	$ 0.08	$ 0.16	$ 0.11
Convertible Senior Notes Due 2024
Denominator:
Warrants (issued in conjunction with Notes due 2024) (in shares)	0	0	2,641	0
Convertible Notes | Convertible Senior Notes Due 2024
Denominator:
Notes due (in shares)	0	0	3,353	0
Convertible Notes | Convertible Senior Notes Due 2023
Denominator:
Notes due (in shares)	0	8,734	900	10,209

NET INCOME (LOSS) PER SHARE -_2

NET INCOME (LOSS) PER SHARE - Schedule of Potentially Dilutive Securities Excluded from the Computation of Diluted Net Income (Loss) Per Share (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	20,770	66	5,755	77
Employee stock-based awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	6,459	66	294	77
Warrants | Convertible Senior Notes Due 2024
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	3,039	0	0	0
Warrants | Convertible Senior Notes Due 2025
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	3,924	0	3,430	0
Notes due | Convertible Senior Notes Due 2024
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	3,677	0	0	0
Notes due | Convertible Senior Notes Due 2025
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	2,771	0	2,031	0
Notes due | Convertible Senior Notes Due 2023
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	900	0	0	0

NET INCOME (LOSS) PER SHARE - N

NET INCOME (LOSS) PER SHARE - Narrative (Details) - Convertible Notes - $ / shares	Mar. 09, 2020	Jun. 05, 2019
Convertible Senior Notes Due 2024
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Debt conversion price (in USD per share)		$ 20.5010
Convertible Senior Notes Due 2025
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Debt conversion price (in USD per share)	$ 81.54

RELATED PARTY - Narrative (Deta

RELATED PARTY - Narrative (Details) - Convertible Notes - Convertible Senior Notes Due 2023 - USD ($)	Jun. 30, 2020	Dec. 31, 2019	Dec. 31, 2018	Aug. 31, 2018
Related Party Transaction [Line Items]
Debt instrument face amount	$ 5,000,000	$ 5,000,000		$ 65,000,000
Thurman John Rodgers
Related Party Transaction [Line Items]
Debt instrument face amount	$ 5,000,000	$ 5,000,000	$ 5,000,000