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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2017	May 05, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	Enphase Energy, Inc.
Entity Central Index Key	0001463101
Document Type	10-Q
Document Period End Date	Mar. 31, 2017
Amendment Flag	false
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q1
Current Fiscal Year End	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		84,276,432

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 29,955	$ 17,764
Accounts receivable, net of allowances of $2,145 and $2,921 at March 31, 2017 and December 31, 2016, respectively	48,903	61,019
Inventory	33,808	31,960
Prepaid expenses and other assets	10,133	7,121
Total current assets	122,799	117,864
Property and equipment, net	30,905	31,440
Goodwill	3,664	3,664
Intangibles, net	806	945
Other assets	9,333	9,663
Total assets	167,507	163,576
Current liabilities:
Accounts payable	15,858	31,696
Accrued liabilities	21,698	22,937
Deferred revenues, current	7,200	6,411
Warranty obligations, current (includes $3,467 and $3,296 measured at fair value at March 31, 2017 and December 31, 2016, respectively)	8,376	8,596
Revolving credit facility	0	10,100
Current portion of term loan	1,497	3,032
Total current liabilities	54,629	82,772
Long-term liabilities:
Deferred revenues, noncurrent	34,499	33,893
Warranty obligations, noncurrent (includes $8,160 and $7,036 measured at fair value at March 31, 2017 and December 31, 2016, respectively)	23,619	22,818
Other liabilities	1,905	2,025
Term loan, less current portion	45,384	20,768
Total liabilities	160,036	162,276
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.00001 par value, 10,000 shares authorized; none issued and outstanding	0	0
Common stock, $0.00001 par value, 100,000 shares authorized; 84,276 and 62,269 shares issued and outstanding at March 31, 2017 and December 31, 2016, respectively	1	1
Additional paid-in capital	281,941	252,126
Accumulated deficit	(273,840)	(250,535)
Accumulated other comprehensive loss	(631)	(292)
Total stockholders’ equity	7,471	1,300
Total liabilities and stockholders’ equity	$ 167,507	$ 163,576

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Allowances, accounts receivable	$ 2,145	$ 2,921
Warranty obligations, current at fair value	3,467	3,296
Warranty obligations, non-current at fair value	$ 8,160	$ 7,036
Common stock, par value (in usd per share)	$ 0.00001	$ 0.00001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	84,276,000	62,269,000
Common stock, shares outstanding (in shares)	84,276,000	62,269,000
Preferred stock, par value (in usd per share)	$ 0.00001	$ 0.00001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Statement [Abstract]
Net revenues	$ 54,751	$ 64,121
Cost of revenues	47,703	52,361
Gross profit	7,048	11,760
Operating expenses:
Research and development	9,605	13,066
Sales and marketing	6,458	10,215
General and administrative	5,833	7,567
Restructuring charges	7,247	0
Total operating expenses	29,143	30,848
Loss from operations	(22,095)	(19,088)
Other income (expense), net:
Interest expense	(2,139)	(152)
Other income	1,060	681
Total other income (expense), net	(1,079)	529
Loss before income taxes	(23,174)	(18,559)
Provision for income taxes	(131)	(236)
Net loss	$ (23,305)	$ (18,795)
Net loss per share:
Net loss per share, basic and diluted (in usd per share)	$ (0.30)	$ (0.41)
Shares used in per share calculation:
Shares used in per share calculation, basic and diluted (in shares)	76,651	46,209

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net loss	$ (23,305)	$ (18,795)
Other comprehensive loss:
Foreign currency translation adjustments	(339)	(194)
Comprehensive loss	$ (23,644)	$ (18,989)

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net loss	$ (23,305)	$ (18,795)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	2,328	2,680
Provision for doubtful accounts	142	537
Asset impairment and restructuring	1,920	25
Amortization of debt issuance costs	945	28
Stock-based compensation	1,929	2,999
Changes in operating assets and liabilities:
Accounts receivable	11,975	(1,494)
Inventory	(1,848)	(4,776)
Prepaid expenses and other assets	(3,114)	(2,062)
Accounts payable, accrued and other liabilities	(17,458)	2,229
Warranty obligations	580	(888)
Deferred revenues	1,395	4,268
Net cash used in operating activities	(24,511)	(15,249)
Cash flows from investing activities:
Purchases of property and equipment	(3,466)	(3,348)
Net cash used in investing activities	(3,466)	(3,348)
Cash flows from financing activities:
Proceeds from issuance of common stock, net of issuance costs	26,522	0
Proceeds from term loan, net	24,162	0
Proceeds from borrowings under revolving credit facility	0	10,000
Payments under revolving credit facility	(10,100)	(7,000)
Payments of deferred financing costs	0	(55)
Proceeds from issuance of common stock under employee stock plans	2	101
Net cash provided by financing activities	40,586	3,046
Effect of exchange rate changes on cash	(418)	115
Net increase (decrease) in cash and cash equivalents	12,191	(15,436)
Cash and cash equivalents—Beginning of period	17,764	28,452
Cash and cash equivalents—End of period	29,955	13,016
Supplemental disclosures of non-cash investing and financing activities:
Purchases of fixed and intangible assets included in accounts payable	1,309	1,691
Deferred debt and offering costs included in accounts payable	231	0
Warrants issued in connection with debt	$ 1,447	$ 0

DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION	3 Months Ended
DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION	Mar. 31, 2017
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. and subsidiaries (the “Company”) delivers simple, innovative and reliable energy management solutions that advance the worldwide potential of renewable energy. Our semiconductor-based microinverter system converts direct current (DC) electricity to alternating current (AC) electricity at the individual solar module level, and brings a system-based, high technology approach to solar energy generation leveraging our design expertise across power electronics, semiconductors, networking, and cloud-based software technologies. Since inception, the Company has shipped more than14 million microinverters, representing over 3 gigawatts of solar photovoltaic (PV) generating capacity, and more than 620,000 Enphase residential and commercial systems have been deployed in over 100 countries. Basis of Presentation and Consolidation The accompanying condensed consolidated financial statements are presented in accordance with accounting principles generally accepted in the 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. The Company disclosed in its Form 10-K for the year ended December 31, 2016 that certain conditions led it to conclude that substantial doubt existed as to the Company’s ability to continue as a going concern. The Company believes that the same or similar conditions continue to exist and that substantial doubt as to its ability to continue as a going concern within one year from the date of this filing also continues to exist. The accompanying consolidated financial statements for the three months ended March 31, 2017 are presented on a going concern basis and do not include any adjustments that might result from the outcome of this uncertainty. The Company has taken actions and intends to take further actions to improve its liquidity, including raising funds in the capital markets. In 2016, the Company completed a public offering of its common stock. The Company sold approximately 15 million shares and realized net proceeds of approximately $16.2 million. In December of 2016, the Company entered into an At The Market Issuance Sales Agreement (ATM) under which it may sell shares of common stock up to a gross aggregate offering price of $17.0 million. The Company realized the full gross proceeds of $17.0 million from common stock sold under the ATM during the three months ended March 31, 2017. In January 2017, the Company completed a private placement of securities that resulted in gross proceeds of $10.0 million. In July 2016, the Company entered into a loan and security agreement (the “Term Loan Agreement”) with lenders that are affiliates of Tennenbaum Capital Partners, LLC (collectively “TCP”). Under the agreement, the lenders committed to advance a term loan in an aggregate principal amount of up to $25.0 million with a maturity date of July 1, 2020. The Company drew down the $25.0 million term loan commitment at closing. In February 2017, the Company amended its loan and security agreement with TCP to provide an additional $25 million in principal. The Company simultaneously terminated its revolving credit facility with Wells Fargo Bank, N.A., and the combined principal and interest balance of $10.3 million was fully repaid. The amended loan has the same July 1, 2020 maturity date as the original TCP loan, both of which are interest only until February 2018. See Note 7, “Debt” for further information. The Company launched its next generation microinverter, the Enphase Home Energy Solution with IQ, in March 2017. This product is a major milestone in the Company’s product cost reduction initiative. The Company also introduced its AC Battery storage system in Australia in the third quarter of 2016 and in the U.S. and Europe in the fourth quarter of 2016. Actions the Company has taken to reduce its operating expenses include a reduction in its global workforce in the third quarter of 2016 and a second reduction in January 2017. The Company has eliminated certain projects that did not have a near-term return on investment, consolidated office space at its headquarters, divested its services business and engaged a management consulting firm to help it improve operational efficiencies. The Company expects the cumulative impact of these actions to decrease its ongoing annualized operating expenses by approximately $40 million as compared to pre-restructuring annualized operating expenses. For the three months ended March 31, 2017, the Company achieved a combined $9.0 million in savings for research and development, sales and marketing and general and administrative expenses over the same period in 2016, which was partially offset by increased restructuring charges of $7.2 million. Unaudited Interim Financial Information These accompanying unaudited condensed consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (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) and cash flows for the interim periods indicated. The results of operations for the three months ended March 31, 2017 are not necessarily indicative of the operating results for the full year. Certain information and footnote disclosures typically included in annual consolidated financial statements have been condensed or omitted. Accordingly, these unaudited interim condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016. There have been no material changes in the Company’s significant accounting policies during the three months ended March 31, 2017, as compared to the significant accounting policies described in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016. Reference is made to the disclosures therein for a summary of all of the Company’s significant accounting policies. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of income and expenses during the reporting period. Significant estimates and assumptions reflected in the financial statements include revenue recognition, inventory valuation and accrued warranty obligations. 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. Recently Adopted Accounting Pronouncements In July 2015, the FASB issued ASU 2015-11, “Simplifying the Measurement of Inventory,” which requires most entities to measure most inventories at the lower of cost or net realizable value ("NRV"). This simplifies the evaluation from the current method of lower of cost or market, where market is based on one of three measures (i.e. replacement cost, net realizable value, or net realizable value less a normal profit margin). ASU 2015-11 does not apply to inventories measured under the last-in, first-out method or the retail inventory method, and defines NRV as the “estimated selling price in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation.” ASU 2015-11 is effective for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years. The adoption of this standard did not have a material impact on the consolidated financial statements. In March 2016, the FASB issued ASU 2016-09, “Improvements to Employee Share-Based Payment Accounting,” which will simplify the income tax consequences, accounting for forfeitures and classification on the Statements of Consolidated Cash Flows. ASU 2016-09 is effective for fiscal years and interim periods beginning after December 15, 2016, with early adoption permitted. The adoption of this standard did not have a material impact on the consolidated financial statements. Recently Issued Accounting Pronouncements Not Yet Effective In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-09, “Revenue from Contracts with Customers,” which will replace most existing revenue recognition guidance under U.S. GAAP. The updated standard’s core principle is that revenue is recognized when promised goods or services are transferred to customers in an amount that reflects the consideration to which an entity expects to be entitled in exchange for those goods or services. The standard generally requires an entity to identify performance obligations in its contracts, estimate the amount of variable consideration to be received in the transaction price, allocate the transaction price to each separate performance obligation, and recognize revenue as obligations are satisfied. In addition, the updated standard requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts. In 2015, the FASB issued guidance to defer the effective date to fiscal years beginning after December 15, 2017 with early adoption for fiscal years beginning December 15, 2016. The guidance permits the use of either a retrospective or cumulative effect transition method. In March 2016, the FASB issued ASU 2016-08, “Revenue from Contracts with Customers: Principal versus Agent Considerations (Reporting Revenue Gross versus Net),” which clarifies the guidance in ASU 2014-09 and has the same effective date as the original standard. During the three months ended June 30, 2016, the FASB issued ASU 2016-10, “Revenue from Contracts with Customers: Identifying Performance Obligations and Licensing”; ASU 2016-11, “Rescission of SEC Guidance Because of Accounting Standards Updates 2014-09 and 2014-16 Pursuant to Staff Announcements at the March 3, 2016 EITF Meeting”; and ASU 2016-12, “Revenue from Contracts with Customers: Narrow-Scope Improvements and Practical Expedients.” These amendments are intended to improve and clarify the implementation guidance of ASU 2014-09 and have the same effective date as the original standard. The Company has not yet selected a transition method and is currently evaluating the impact of adoption on the consolidated financial statements. In January 2016, the FASB issued ASU 2016-01, “Recognition and Measurement of Financial Assets and Financial Liabilities,” which amends certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. Changes to the current guidance include the accounting for equity investments, the presentation and disclosure requirements for financial instruments, and the assessment of valuation allowance on deferred tax assets related to available-for-sale securities. In addition, ASU 2016-01 establishes an incremental recognition and disclosure requirement related to the presentation of fair value changes of financial liabilities for which the fair value option has been elected. Under this guidance, an entity would be required to separately present in other comprehensive income the portion of the total fair value change attributable to instrument-specific credit risk as opposed to reflecting the entire amount in earnings. ASU 2016-01 is effective for fiscal years and interim periods beginning after December 15, 2017, and upon adoption, an entity should apply the amendments by means of a cumulative-effect adjustment to the balance sheet at the beginning of the first reporting period in which the guidance is effective. Early adoption is not permitted except for the provision to record fair value changes for financial liabilities under the fair value option resulting from instrument-specific credit risk in other comprehensive income. The Company is currently evaluating the impact of adoption on the consolidated financial statements.

INVENTORY

3 Months Ended

Mar. 31, 2017

Inventory Disclosure [Abstract]

INVENTORY

Inventory as of March 31, 2017 and December 31, 2016 consists of the following (in thousands):



	March 31, 2017		December 31, 2016
Raw materials	$	3,229	$	5,095
Finished goods	30,579		26,865
Total inventory	$	33,808	$	31,960

WARRANTY OBLIGATIONS

3 Months Ended

Mar. 31, 2017

Product Warranties Disclosures [Abstract]

WARRANTY OBLIGATIONS

The Company’s warranty activities during the three months ended March 31, 2017 and 2016 were as follows (in thousands):



	Three Months Ended March 31,
	2017			2016
Warranty obligations, beginning of period	$	31,414		$	30,547
Accruals for warranties issued during period	834			708
Changes in estimates	291			158
Settlements	(1,617		)	(1,719		)
Increase due to accretion expense	495			384
Other	578			(419		)
Warranty obligations, end of period	$	31,995		$	29,659
Less current portion	$	(8,376	)	$	(6,651	)
Noncurrent	$	23,619		$	23,008

As of March 31, 2017, the $32.0 million of warranty obligations included $11.6 million measured at fair value. See Note 4, “Fair Value Measurements” for additional information.

FAIR VALUE MEASUREMENTS

3 Months Ended

Mar. 31, 2017

Fair Value Disclosures [Abstract]

FAIR VALUE MEASUREMENTS

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

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


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


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


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

The following table presents the Company’s liabilities that were measured at fair value on a recurring basis and its categorization within the fair value hierarchy at March 31, 2017 and December 31, 2016 (in thousands):



	Fair Value Hierarchy	March 31, 2017		December 31, 2016
Liabilities:
Warranty obligations	Level 3	$	11,627	$	10,332

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

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

The Company estimates the fair value of warranty obligations by calculating the warranty obligations in the same manner as for sales prior to January 1, 2014 and applying an expected present value technique to that result. The expected present value technique, an income approach, converts future amounts into a single current discounted amount. In addition to the key estimates of failure rates, claim rates and replacement costs, the Company used certain 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 (in thousands):



	Three Months Ended March 31,
	2017			2016
Balance at beginning of period	$	10,332		$	6,182
Accruals for warranties issued during period	830			695
Changes in estimates	(266		)	(199		)
Settlements	(342		)	(154		)
Increase due to accretion expense	495			384
Other	578			(419		)
Balance at end of period	$	11,627		$	6,489

Quantitative and Qualitative Information about Level 3 Fair Value Measurements

As of March 31, 2017, the significant unobservable inputs used in the fair value measurement of the Company’s liabilities designated as Level 3 are as follows:



Item Measured at Fair Value	Valuation Technique	Description of Significant Unobservable Input	Percent Used (Weighted-Average)
Warranty obligations for microinverters sold since January 1, 2014	Discounted cash flows	Profit element and risk premium	17%
	Discounted cash flows	Credit-adjusted risk-free rate	18%

As of December 31, 2016, the significant unobservable inputs used in the fair value measurement of the Company’s liabilities designated as Level 3 are as follows:



Item Measured at Fair Value	Valuation Technique	Description of Significant Unobservable Input	Percent Used (Weighted-Average)
Warranty obligations for microinverters sold since January 1, 2014	Discounted cash flows	Profit element and risk premium	17%
	Discounted cash flows	Credit-adjusted risk-free rate	19%

Sensitivity of Level 3 Inputs

Warranty Obligations

Each of the significant unobservable inputs is independent of the other. The profit element and risk premium are estimated based on requirements of a third-party participant willing to assume the Company’s warranty obligations. The credit-adjusted risk free rate (“discount rate”) is determined by reference to the Company’s own credit standing at the fair value measurement date. Increasing or decreasing the profit element and risk premium input by 100 basis points would not have a material impact on the fair value measurement of the liability. Increasing the discount rate by 100 basis points would result in a $0.5 million reduction of the liability. Decreasing the discount rate by 100 basis points would result in a $0.5 million increase to the liability.

- Definition

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

+ References + Details

GOODWILL AND INTANGIBLE ASSETS

3 Months Ended

Mar. 31, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

GOODWILL AND INTANGIBLE ASSETS

The following table presents the details of the Company’s goodwill and purchased intangible assets as of March 31, 2017 and December 31, 2016 (in thousands):



	March 31, 2017							December 31, 2016
	Gross		Accumulated Amortization			Net		Gross		Accumulated Amortization			Net
Goodwill	$	3,664	$	—		$	3,664	$	3,664	$	—		$	3,664

Other indefinite-lived intangibles	$	286	$	—		$	286	$	286	$	—		$	286

Intangible assets with finite lives:
Patents and licensed technology	$	1,665	$	(1,145	)	$	520	$	1,665	$	(1,006	)	$	659
Total	$	1,665	$	(1,145	)	$	520	$	1,665	$	(1,006	)	$	659

In July 2014, the Company purchased certain patents related to system interconnection and photovoltaic AC module construction. The patents are being amortized over their legal life of 3 years. In October 2015, the Company licensed certain technology related to ASIC development for a 3 year term, which is also its estimated useful life.

For the three months ended March 31, 2017, amortization expense related to intangible assets was $0.1 million. As of March 31, 2017, estimated future amortization expense related to finite-lived intangible assets was as follows:



Year	(In thousands)
2017	$	416
2018	104
Total	$	520

- Definition

The entire disclosure for the aggregate amount of goodwill and a description of intangible assets, which may include (a) for amortizable intangible assets (also referred to as finite-lived intangible assets), the carrying amount, the amount of any significant residual value, and the weighted-average amortization period, (b) for intangible assets not subject to amortization (also referred to as indefinite-lived intangible assets), the carrying amount, and (c) the amount of research and development assets acquired and written off in the period, including the line item in the income statement in which the amounts written off are aggregated, if not readily apparent from the income statement. Also discloses (a) for amortizable intangibles assets in total and by major class, the gross carrying amount and accumulated amortization, the total amortization expense for the period, and the estimated aggregate amortization expense for each of the five succeeding fiscal years, (b) for intangible assets not subject to amortization the carrying amount in total and by major class, and (c) for goodwill, in total and for each reportable segment, the changes in the carrying amount of goodwill during the period (including the aggregate amount of goodwill acquired, the aggregate amount of impairment losses recognized, and the amount of goodwill included in the gain (loss) on disposal of a reporting unit). If any part of goodwill has not been allocated to a reportable segment, discloses the unallocated amount and the reasons for not allocating. For each impairment loss recognized related to an intangible asset (excluding goodwill), discloses: (a) a description of the impaired intangible asset and the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method for determining fair value, (c) the caption in the income statement or the statement of activities in which the impairment loss is aggregated, and (d) the segment in which the impaired intangible asset is reported. For each goodwill impairment loss recognized, discloses: (a) a description of the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method of determining the fair value of the associated reporting unit, and (c) if a recognized impairment loss is an estimate not finalized and the reasons why the estimate is not final. May also disclose the nature and amount of any significant adjustments made to a previous estimate of an impairment loss.

+ References + Details

RESTRUCTURING

3 Months Ended

Mar. 31, 2017

Restructuring and Related Activities [Abstract]

RESTRUCTURING

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

The following table presents the details of the Company’s restructuring charges for the periods indicated (in thousands):



	Three Months Ended March 31,
	2017		2016
Employee severance and benefit arrangements	$	1,592	$	—
Asset impairments	522		—
Consultants engaged in restructuring activities	4,000		—
Lease loss reserves and contract termination costs	1,133		—
Total restructuring and asset impairment charges	$	7,247	$	—

The following table provides information regarding changes in the Company’s accrued restructuring balance for the periods indicated (in thousands):



	Employee Severance and Benefits			Asset Impairments			Lease Loss Reserves and Contractual Obligations			Total
Balance at beginning of period as of December 31, 2016	$	198		$	—		$	484		$	682
Charges	1,592			522			5,133			7,247
Cash payments	(1,641		)	—			(4,230		)	(5,871		)
Non-cash settlement	—			(522		)				(522		)
Balance at end of period as of March 31, 2017	$	149		$	—		$	1,387		$	1,536

DEBT

3 Months Ended

Mar. 31, 2017

Short-term Debt [Abstract]

DEBT

Revolving Credit Facility

The Company had a $50.0 million revolving credit facility with Wells Fargo Bank, N.A. (“Wells Fargo”) that was entered into in November 2012, as first amended on February 14, 2014. On December 18, 2015, the Company entered into an amended and restated revolving credit agreement with Wells Fargo (the “Revolver”) which extended the maturity date to November 7, 2019 and added an uncommitted accordion feature that could increase the size of the facility by $25.0 million, subject to the satisfaction of certain conditions. The Revolver was fully repaid and terminated in February 2017.

Term Loan

In July 2016, the Company entered into a Term Loan Agreement (the “Original Term Loan”) with lenders that are affiliates of Tennenbaum Capital Partners, LLC. (the “Lenders”). Under the agreement, the Lenders committed to advance a term loan in an aggregate principal amount of up to $25.0 million with a maturity date of July 1, 2020. The Company borrowed the entire $25.0 million of term loan commitments on the loan closing date. Monthly payments due through June 30, 2017 were interest only, followed by consecutive equal monthly payments of principal plus accrued interest that were to begin on July 1, 2017 and continue through the maturity date. The term loan provides for an interest rate per annum equal to the higher of (i) 10.25% or (ii) LIBOR plus 9.5625%, subject to a 1.0% reduction if the Company achieves minimum levels of Revenue and EBITDA (each as defined in the Term Loan Agreement) for the twelve-consecutive month period ending June 30, 2017 as set forth in the Term Loan Agreement. In addition, the Company paid a commitment fee of 3.3% of the loan amount upon closing and a closing fee of 10.0% of the loan amount is payable in four equal installments at each anniversary of the closing date. The Company may elect to prepay the loan by incurring a prepayment fee between 1% and 3% of the principal amount of the term loan depending on the timing and circumstances of prepayment.

In February 2017, the Company entered into an Amended and Restated Loan and Security Agreement (the “Loan Agreement”) that amended and restated the Original Term Loan. The Loan Agreement provides for a $25.0 million secured term loan to the Company (the “New Term Loan”), which is in addition to the $25.0 million secured term loan borrowed by the Company under the Original Term Loan (together with the “New Term Loan” the “Term Loans”). The New Term Loan has the same July 1, 2020 maturity date that was applicable to the Original Term Loan. The New Term Loan was fully drawn at closing, with approximately $10.3 million of the proceeds used to repay existing combined principal and interest due under the Company’s Revolver with Wells Fargo. Upon the repayment of loans under the Wells Fargo Revolver, the Wells Fargo Revolving Credit Agreement was terminated. The Company expects to use the remainder of the proceeds from the New Term Loan for general corporate purposes.

Monthly payments under the Term Loans through February 28, 2018 are interest only, followed by consecutive equal monthly payments of principal plus accrued interest beginning on March 1, 2018 and continuing through the maturity date; provided, however, that the Company may extend the interest only period on a month to month basis up to February 28, 2019 if no Event of Default (as defined in the Loan Agreement) has occurred and is continuing and the Company has Consolidated Operating Income (as defined in the Loan Agreement) for the calendar year 2017 and each month thereafter on a trailing twelve consecutive month basis of at least $15.0 million (collectively, the “Accommodation Conditions”). The Term Loans provide for an interest rate per annum equal to the greater of (i) 10.3125% and (ii) LIBOR plus 9.25%, subject to a 1.0% reduction if and for so long as the Accommodation Conditions have been met. In addition, the Company paid a commitment fee of 3.0% of the New Term Loan amount upon closing and a closing fee of 4.0% of the New Term Loan amount, which is payable with the closing fee under the Original Term Loan in four equal installments at each anniversary of the closing date of the Original Loan Agreement. The Company may elect to prepay the Term Loans by incurring a prepayment fee between 1% and 3% of the principal amount of the Term Loans depending on the timing and circumstances of prepayment.

The Term Loans are secured by a first-priority security interest on substantially all assets of the Company; provided, however that the security interest in the Company’s intellectual property may be released if the Company satisfies certain requirements. The Company’s obligations under the Term Loans are not guaranteed by any of the Company’s existing subsidiaries, nor have any existing subsidiaries of the Company pledged any of their assets to secure the Term Loans.

The Loan Agreement requires that (i) at all times from the closing date to and including March 31, 2018, the Company, and any future guarantors, have Unrestricted Cash (as defined in the Loan Agreement) of at least $10.0 million; (ii) at all times from the closing date to and including March 31, 2018, that the aggregate amount of Consolidated Unrestricted Cash, plus the value of Consolidated Receivables, plus the value of Consolidated Inventory (each as defined in the Loan Agreement) divided by the outstanding principal amount of Term Loans, shall equal or exceed 1.5; and (iii) at all times from April 1, 2018 and thereafter, that the aggregate amount of Consolidated Unrestricted Cash, plus the value of Consolidated Receivables, plus the value of Consolidated Inventory divided by the outstanding principal amount of Term Loans, shall equal or exceed 1.75. In addition, the Loan Agreement is subject to customary affirmative and negative covenants including restrictions on creation of liens, dispositions of assets, mergers, changing the nature of its business and dividends and other distributions, in each case subject to certain exceptions. The Term Loan Agreement also contains certain customary events of default including, but not limited to, failure to pay interest, principal and fees or other amounts when due, material breach of any representation or warranty, covenant defaults, cross defaults to other material indebtedness, events of bankruptcy and the occurrence of a material adverse change (as defined in the agreement) to the Company’s business. The Term Loan Agreement offers TCP typical rights and remedies in any event of default, including the ability to declare all amounts outstanding immediately due and payable. The Company was in compliance with all financial covenants as of March 31, 2017.

In connection with the New Term Loan, the Company issued to the Lenders warrants to purchase an aggregate 1,220,000 shares of the Company’s Common Stock at an exercise price of $1.05 per share. The warrants have a term of seven years and contain a “cashless exercise” feature that allows the holder to exercise the warrant without a cash payment upon the terms set forth therein.

The Company estimated the fair value of the warrants by using the Black-Scholes approach and the following assumptions: stock price of $1.56; strike price of $1.05; volatility of 85.9%, risk-free rate of 2.23%; dividend yield of 0%; and a 7 year term. The resulting fair value was used to allocate the proceeds from the Term Loan between liability and equity components.

The Company classified the warrants as equity and allocated the proceeds from the Term Loan and warrants using the relative fair value method. Using this method, the Company allocated $1.4 million to the warrants, which was recorded as equity. This amount represents debt discount that will be amortized to interest expense over the term of the loan.

Long-term debt was comprised of the following at March 31, 2017 and December 31, 2016 (in thousands):



	March 31, 2017			December 31, 2016
Term loan	$	50,000		$	25,000
Less unamortized discount and issuance costs	(3,119		)	(1,200		)
Carrying amount of debt	46,881			23,800
Less current portion	(1,497		)	(3,032		)
Long-term debt	$	45,384		$	20,768

As of March 31, 2017, the amount of scheduled principal payments due on the term loan is as follows (in thousands):



Year	Amounts
2017	$	—
2018	15,229
2019	20,084
2020	14,687
Total	$	50,000

COMMITMENTS AND CONTINGENCIES	3 Months Ended
COMMITMENTS AND CONTINGENCIES	Mar. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES The Company is not currently involved in any material legal proceedings. The Company may become involved in various legal proceedings and claims that arise in the ordinary course of business. Such matters are subject to uncertainty and there can be no assurance that such legal proceedings will not have a material adverse effect on its business, results of operations, financial position or cash flows.

SALE OF COMMON STOCK	3 Months Ended
SALE OF COMMON STOCK	Mar. 31, 2017
Equity [Abstract]
SALE OF COMMON STOCK	SALE OF COMMON STOCK In January 2017, the Company completed a private placement of securities that resulted in the issuance of approximately 10.8 million shares of common stock and gross proceeds of $10.0 million. In December of 2016, the Company entered into an At Market Issuance Sales Agreement (ATM) under which it could sell shares of its common stock up to a gross aggregate offering price of $17.0 million. During the three months ended March 31, 2017 the Company sold approximately 11.1 million shares of common stock under the ATM and received net proceeds of approximately $16.6 million.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

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-Name Accounting Standards Codification
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+ Details

STOCK-BASED COMPENSATION

3 Months Ended

Mar. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

STOCK-BASED COMPENSATION

The Company has adopted certain equity incentive and stock purchase plans as described in the consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016.

Equity Awards Activity

Stock Options

The following is a summary of stock option activity for the three months ended March 31, 2017 (in thousands, except per share data):



	Number of Shares Outstanding		Weighted- Average Exercise Price per Share
Outstanding at December 31, 2016	8,730		$	4.56
Granted	191		1.15
Exercised	(6	)	0.42
Canceled	(812	)	6.50
Outstanding at March 31, 2017	8,103		$	4.29

The intrinsic value of options exercised in the three months ended March 31, 2017 was minimal. As of March 31, 2017, the intrinsic value of options outstanding was $1.3 million based on the closing price of the Company’s stock as of March 31, 2017.

Restricted Stock Units

The following is a summary of restricted stock unit activity for the three months ended March 31, 2017 (in thousands, except per share data):



	RSUs		Weighted Average Fair Value per Share at Grant Date
Outstanding at December 31, 2016	606		$	9.33
Granted	—
Vested	(146	)	9.21
Canceled	(40	)	11.60
Outstanding at March 31, 2017	420		$	9.16

The total intrinsic value of restricted stock units that were vested in the three months ended March 31, 2017 was $0.2 million. As of March 31, 2017, the intrinsic value of restricted stock units outstanding was $0.6 million based on the closing price of the Company’s stock as of March 31, 2017.

Stock-Based Compensation Expense

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 (in thousands):



	Three Months Ended March 31,
	2017		2016
Cost of revenues	$	239	$	307
Research and development	751		1,127
Sales and marketing	378		612
General and administrative	561		953
Total	$	1,929	$	2,999

The following table summarizes the various types of stock-based compensation expense for the periods presented (in thousands):



	Three Months Ended March 31,
	2017		2016
Stock options and restricted stock units	$	1,599	$	2,484
Employee stock purchase plan	330		515
Total	$	1,929	$	2,999

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 March 31,
	2017			2016
Weighted average grant date fair value	$	0.68		$	1.28
Expected term (in years)	4.0			4.6
Expected volatility	83.6		%	77.4		%
Annual risk-free rate of return	1.7		%	1.2		%
Dividend yield	0.0		%	0.0		%

As of March 31, 2017, there was approximately $7.5 million of total unrecognized compensation expense related to unvested equity awards expected to be recognized over a weighted-average period of 2.4 years.

- Definition

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

+ References + Details

INCOME TAXES	3 Months Ended
INCOME TAXES	Mar. 31, 2017
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The Company used the discrete tax approach in calculating the tax expense for the three months ended March 31, 2017 and 2016 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 LOSS PER SHARE

3 Months Ended

Mar. 31, 2017

Earnings Per Share [Abstract]

NET LOSS PER SHARE

Basic net loss per share is computed by dividing net loss by the weighted average number of shares of common stock outstanding during the period. Diluted 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 outstanding in-the-money stock options, restricted stock units, shares to be purchased under the Company’s employee stock purchase plan and warrants to purchase common stock. The dilutive effect of potentially dilutive common shares is reflected in diluted earnings per share by application of the treasury stock method. To the extent these potential common shares are antidilutive, they are excluded from the calculation of diluted net loss per share.

The following table presents the computation of basic and diluted net loss per share for the periods presented (in thousands, except per share data):



	Three Months Ended March 31,
	2017			2016
Numerator:
Net loss	$	(23,305	)	$	(18,795	)

Denominator:
Weighted average common shares outstanding	76,651			46,209

Net loss per share, basic and diluted	$	(0.30	)	$	(0.41	)

As the Company incurred a net loss for all periods presented, potential dilutive securities from employee stock options, restricted stock units and warrants have been excluded from the diluted net loss per share computations because the effect of including such shares would have been anti-dilutive. The following table sets forth the potentially dilutive securities excluded from the computation of the diluted net loss per share (in thousands):



	Three Months Ended March 31,
	2017	2016
Employee stock options	8,458	8,160
Restricted stock units	526	1,164
Warrants to purchase common stock	664	111
Total	9,648	9,435

DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION (Policies)	3 Months Ended
	Mar. 31, 2017
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 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	Unaudited Interim Financial Information These accompanying unaudited condensed consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (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) and cash flows for the interim periods indicated. The results of operations for the three months ended March 31, 2017 are not necessarily indicative of the operating results for the full year. Certain information and footnote disclosures typically included in annual consolidated financial statements have been condensed or omitted. Accordingly, these unaudited interim condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016.
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, inventory valuation and accrued warranty obligations. 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.
Recently Adopted Accounting Pronouncements and Recently Issued Accounting Pronouncements Not Yet Effective	Recently Adopted Accounting Pronouncements In July 2015, the FASB issued ASU 2015-11, “Simplifying the Measurement of Inventory,” which requires most entities to measure most inventories at the lower of cost or net realizable value ("NRV"). This simplifies the evaluation from the current method of lower of cost or market, where market is based on one of three measures (i.e. replacement cost, net realizable value, or net realizable value less a normal profit margin). ASU 2015-11 does not apply to inventories measured under the last-in, first-out method or the retail inventory method, and defines NRV as the “estimated selling price in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation.” ASU 2015-11 is effective for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years. The adoption of this standard did not have a material impact on the consolidated financial statements. In March 2016, the FASB issued ASU 2016-09, “Improvements to Employee Share-Based Payment Accounting,” which will simplify the income tax consequences, accounting for forfeitures and classification on the Statements of Consolidated Cash Flows. ASU 2016-09 is effective for fiscal years and interim periods beginning after December 15, 2016, with early adoption permitted. The adoption of this standard did not have a material impact on the consolidated financial statements. Recently Issued Accounting Pronouncements Not Yet Effective In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-09, “Revenue from Contracts with Customers,” which will replace most existing revenue recognition guidance under U.S. GAAP. The updated standard’s core principle is that revenue is recognized when promised goods or services are transferred to customers in an amount that reflects the consideration to which an entity expects to be entitled in exchange for those goods or services. The standard generally requires an entity to identify performance obligations in its contracts, estimate the amount of variable consideration to be received in the transaction price, allocate the transaction price to each separate performance obligation, and recognize revenue as obligations are satisfied. In addition, the updated standard requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts. In 2015, the FASB issued guidance to defer the effective date to fiscal years beginning after December 15, 2017 with early adoption for fiscal years beginning December 15, 2016. The guidance permits the use of either a retrospective or cumulative effect transition method. In March 2016, the FASB issued ASU 2016-08, “Revenue from Contracts with Customers: Principal versus Agent Considerations (Reporting Revenue Gross versus Net),” which clarifies the guidance in ASU 2014-09 and has the same effective date as the original standard. During the three months ended June 30, 2016, the FASB issued ASU 2016-10, “Revenue from Contracts with Customers: Identifying Performance Obligations and Licensing”; ASU 2016-11, “Rescission of SEC Guidance Because of Accounting Standards Updates 2014-09 and 2014-16 Pursuant to Staff Announcements at the March 3, 2016 EITF Meeting”; and ASU 2016-12, “Revenue from Contracts with Customers: Narrow-Scope Improvements and Practical Expedients.” These amendments are intended to improve and clarify the implementation guidance of ASU 2014-09 and have the same effective date as the original standard. The Company has not yet selected a transition method and is currently evaluating the impact of adoption on the consolidated financial statements. In January 2016, the FASB issued ASU 2016-01, “Recognition and Measurement of Financial Assets and Financial Liabilities,” which amends certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. Changes to the current guidance include the accounting for equity investments, the presentation and disclosure requirements for financial instruments, and the assessment of valuation allowance on deferred tax assets related to available-for-sale securities. In addition, ASU 2016-01 establishes an incremental recognition and disclosure requirement related to the presentation of fair value changes of financial liabilities for which the fair value option has been elected. Under this guidance, an entity would be required to separately present in other comprehensive income the portion of the total fair value change attributable to instrument-specific credit risk as opposed to reflecting the entire amount in earnings. ASU 2016-01 is effective for fiscal years and interim periods beginning after December 15, 2017, and upon adoption, an entity should apply the amendments by means of a cumulative-effect adjustment to the balance sheet at the beginning of the first reporting period in which the guidance is effective. Early adoption is not permitted except for the provision to record fair value changes for financial liabilities under the fair value option resulting from instrument-specific credit risk in other comprehensive income. The Company is currently evaluating the impact of adoption on the consolidated financial statements.
Income Taxes	The Company used the discrete tax approach in calculating the tax expense for the three months ended March 31, 2017 and 2016 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.

- Definition

Disclosure of accounting policy for income taxes, which may include its accounting policies for recognizing and measuring deferred tax assets and liabilities and related valuation allowances, recognizing investment tax credits, operating loss carryforwards, tax credit carryforwards, and other carryforwards, methodologies for determining its effective income tax rate and the characterization of interest and penalties in the financial statements.

+ References + Details

INVENTORY (Tables)

3 Months Ended

Mar. 31, 2017

Inventory Disclosure [Abstract]

Summary of Inventory

Inventory as of March 31, 2017 and December 31, 2016 consists of the following (in thousands):



	March 31, 2017		December 31, 2016
Raw materials	$	3,229	$	5,095
Finished goods	30,579		26,865
Total inventory	$	33,808	$	31,960

WARRANTY OBLIGATIONS (Tables)

3 Months Ended

Mar. 31, 2017

Product Warranties Disclosures [Abstract]

Summary of Warranty Activities

The Company’s warranty activities during the three months ended March 31, 2017 and 2016 were as follows (in thousands):



	Three Months Ended March 31,
	2017			2016
Warranty obligations, beginning of period	$	31,414		$	30,547
Accruals for warranties issued during period	834			708
Changes in estimates	291			158
Settlements	(1,617		)	(1,719		)
Increase due to accretion expense	495			384
Other	578			(419		)
Warranty obligations, end of period	$	31,995		$	29,659
Less current portion	$	(8,376	)	$	(6,651	)
Noncurrent	$	23,619		$	23,008

FAIR VALUE MEASUREMENTS (Tables)

3 Months Ended

Mar. 31, 2017

Fair Value Disclosures [Abstract]

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



	Fair Value Hierarchy	March 31, 2017		December 31, 2016
Liabilities:
Warranty obligations	Level 3	$	11,627	$	10,332

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



	Three Months Ended March 31,
	2017			2016
Balance at beginning of period	$	10,332		$	6,182
Accruals for warranties issued during period	830			695
Changes in estimates	(266		)	(199		)
Settlements	(342		)	(154		)
Increase due to accretion expense	495			384
Other	578			(419		)
Balance at end of period	$	11,627		$	6,489

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

As of March 31, 2017, the significant unobservable inputs used in the fair value measurement of the Company’s liabilities designated as Level 3 are as follows:



Item Measured at Fair Value	Valuation Technique	Description of Significant Unobservable Input	Percent Used (Weighted-Average)
Warranty obligations for microinverters sold since January 1, 2014	Discounted cash flows	Profit element and risk premium	17%
	Discounted cash flows	Credit-adjusted risk-free rate	18%

As of December 31, 2016, the significant unobservable inputs used in the fair value measurement of the Company’s liabilities designated as Level 3 are as follows:



Item Measured at Fair Value	Valuation Technique	Description of Significant Unobservable Input	Percent Used (Weighted-Average)
Warranty obligations for microinverters sold since January 1, 2014	Discounted cash flows	Profit element and risk premium	17%
	Discounted cash flows	Credit-adjusted risk-free rate	19%

GOODWILL AND INTANGIBLE ASSETS (Tables)

3 Months Ended

Mar. 31, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Goodwill and Intangible Assets

The following table presents the details of the Company’s goodwill and purchased intangible assets as of March 31, 2017 and December 31, 2016 (in thousands):



	March 31, 2017							December 31, 2016
	Gross		Accumulated Amortization			Net		Gross		Accumulated Amortization			Net
Goodwill	$	3,664	$	—		$	3,664	$	3,664	$	—		$	3,664

Other indefinite-lived intangibles	$	286	$	—		$	286	$	286	$	—		$	286

Intangible assets with finite lives:
Patents and licensed technology	$	1,665	$	(1,145	)	$	520	$	1,665	$	(1,006	)	$	659
Total	$	1,665	$	(1,145	)	$	520	$	1,665	$	(1,006	)	$	659

Schedule of Estimated Future Amortization Expense Related to Finite-Lived Intangible Assets

As of March 31, 2017, estimated future amortization expense related to finite-lived intangible assets was as follows:



Year	(In thousands)
2017	$	416
2018	104
Total	$	520

RESTRUCTURING (Tables)

3 Months Ended

Mar. 31, 2017

Restructuring and Related Activities [Abstract]

Restructuring and Related Costs

The following table presents the details of the Company’s restructuring charges for the periods indicated (in thousands):



	Three Months Ended March 31,
	2017		2016
Employee severance and benefit arrangements	$	1,592	$	—
Asset impairments	522		—
Consultants engaged in restructuring activities	4,000		—
Lease loss reserves and contract termination costs	1,133		—
Total restructuring and asset impairment charges	$	7,247	$	—

Schedule of Restructuring Reserve by Type of Cost

The following table provides information regarding changes in the Company’s accrued restructuring balance for the periods indicated (in thousands):



	Employee Severance and Benefits			Asset Impairments			Lease Loss Reserves and Contractual Obligations			Total
Balance at beginning of period as of December 31, 2016	$	198		$	—		$	484		$	682
Charges	1,592			522			5,133			7,247
Cash payments	(1,641		)	—			(4,230		)	(5,871		)
Non-cash settlement	—			(522		)				(522		)
Balance at end of period as of March 31, 2017	$	149		$	—		$	1,387		$	1,536

DEBT - (Tables)

3 Months Ended

Mar. 31, 2017

Debt Disclosure [Abstract]

Schedule of Debt

Long-term debt was comprised of the following at March 31, 2017 and December 31, 2016 (in thousands):



	March 31, 2017			December 31, 2016
Term loan	$	50,000		$	25,000
Less unamortized discount and issuance costs	(3,119		)	(1,200		)
Carrying amount of debt	46,881			23,800
Less current portion	(1,497		)	(3,032		)
Long-term debt	$	45,384		$	20,768

Schedule of Maturities of Long-term Debt

As of March 31, 2017, the amount of scheduled principal payments due on the term loan is as follows (in thousands):



Year	Amounts
2017	$	—
2018	15,229
2019	20,084
2020	14,687
Total	$	50,000

STOCK-BASED COMPENSATION (Tables)

3 Months Ended

Mar. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Stock Option Activity

The following is a summary of stock option activity for the three months ended March 31, 2017 (in thousands, except per share data):



	Number of Shares Outstanding		Weighted- Average Exercise Price per Share
Outstanding at December 31, 2016	8,730		$	4.56
Granted	191		1.15
Exercised	(6	)	0.42
Canceled	(812	)	6.50
Outstanding at March 31, 2017	8,103		$	4.29

Summary of Restricted Stock Unit Activity

The following is a summary of restricted stock unit activity for the three months ended March 31, 2017 (in thousands, except per share data):



	RSUs		Weighted Average Fair Value per Share at Grant Date
Outstanding at December 31, 2016	606		$	9.33
Granted	—
Vested	(146	)	9.21
Canceled	(40	)	11.60
Outstanding at March 31, 2017	420		$	9.16

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 (in thousands):



	Three Months Ended March 31,
	2017		2016
Cost of revenues	$	239	$	307
Research and development	751		1,127
Sales and marketing	378		612
General and administrative	561		953
Total	$	1,929	$	2,999

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 (in thousands):



	Three Months Ended March 31,
	2017		2016
Stock options and restricted stock units	$	1,599	$	2,484
Employee stock purchase plan	330		515
Total	$	1,929	$	2,999

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



	Three Months Ended March 31,
	2017			2016
Weighted average grant date fair value	$	0.68		$	1.28
Expected term (in years)	4.0			4.6
Expected volatility	83.6		%	77.4		%
Annual risk-free rate of return	1.7		%	1.2		%
Dividend yield	0.0		%	0.0		%

NET LOSS PER SHARE (Tables)

3 Months Ended

Mar. 31, 2017

Earnings Per Share [Abstract]

Schedule of Computation of Basic and Diluted Net Loss Per Share

The following table presents the computation of basic and diluted net loss per share for the periods presented (in thousands, except per share data):



	Three Months Ended March 31,
	2017			2016
Numerator:
Net loss	$	(23,305	)	$	(18,795	)

Denominator:
Weighted average common shares outstanding	76,651			46,209

Net loss per share, basic and diluted	$	(0.30	)	$	(0.41	)

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

The following table sets forth the potentially dilutive securities excluded from the computation of the diluted net loss per share (in thousands):



	Three Months Ended March 31,
	2017	2016
Employee stock options	8,458	8,160
Restricted stock units	526	1,164
Warrants to purchase common stock	664	111
Total	9,648	9,435

DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION (Details) system in Thousands, deliverable in Millions, watt in Billions	1 Months Ended			3 Months Ended		12 Months Ended
	Jan. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($)	Jul. 31, 2016 USD ($)	Mar. 31, 2017 USD ($) system country deliverable watt shares	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($) shares	Feb. 28, 2017 USD ($)
Product Information [Line Items]
Proceeds from issuance of common stock, net of issuance costs				$ 26,522,000	$ 0
Proceeds from term loan, net				24,162,000	0
Payments under revolving credit facility				10,100,000	$ 7,000,000
Combined savings				9,000,000
Restructuring charges				$ 7,200,000
Microinverter
Product Information [Line Items]
Number of product shipped \| deliverable				14
Number of watts \| watt				3
Residential And Commercial Systems
Product Information [Line Items]
Number of product deployed \| system				620
Number of countries in which product is deployed \| country				100
Reduction in Annualized Operating Expense
Product Information [Line Items]
Expected decrease in annualized expenses				$ 40,000,000
Over-Allotment Option
Product Information [Line Items]
Proceeds from issuance of common stock, net of issuance costs						$ 16,200,000
Market Issuance Sales Agreement (ATM)
Product Information [Line Items]
Common stock issued during period (in shares) \| shares				11,100,000
Proceeds from issuance of common stock, net of issuance costs				$ 16,600,000
Gross aggregate offering price		$ 17,000,000
Gross proceeds from issuance of common stock				$ 17,000,000
Private Placement
Product Information [Line Items]
Common stock issued during period (in shares) \| shares	10,800,000.0
Proceeds from issuance of common stock, net of issuance costs	$ 10,000,000
Gross proceeds from issuance of common stock	$ 10,000,000
Term Loan Agreement, July 2016 \| Secured Debt \| Tennenbaum Capital Partners, LLC
Product Information [Line Items]
Debt instrument face amount			$ 25,000,000.0
Proceeds from term loan, net			25,000,000
Revolving Credit Facility \| Line of Credit \| Wells Fargo Bank
Product Information [Line Items]
Payments under revolving credit facility			10,300,000
Secured Debt \| Tennenbaum Capital Partners, LLC
Product Information [Line Items]
Debt instrument face amount			25,000,000.0
Proceeds from term loan, net			$ 25,000,000
Secured Debt \| Amended Term Loan Agreement, February 2017 \| Tennenbaum Capital Partners, LLC
Product Information [Line Items]
Debt instrument face amount							$ 25,000,000.0
Common Stock \| Over-Allotment Option
Product Information [Line Items]
Common stock issued during period (in shares) \| shares						15,000,000

INVENTORY - Summary of Inventory (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Schedule of inventory
Raw materials	$ 3,229	$ 5,095
Finished goods	30,579	26,865
Total inventory	$ 33,808	$ 31,960

WARRANTY OBLIGATIONS - Summary of Warranty Activities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Changes in the Company's product warranty liability
Warranty obligations, beginning of period	$ 31,414	$ 30,547
Accruals for warranties issued during period	834	708
Changes in estimates	291	158
Settlements	(1,617)	(1,719)
Increase due to accretion expense	495	384
Other	578	(419)
Warranty obligations, end of period	31,995	29,659
Less current portion	(8,376)	(6,651)	$ (8,596)
Noncurrent	$ 23,619	$ 23,008	$ 22,818

WARRANTY OBLIGATIONS - Narrative (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Product Warranty Liability [Line Items]
Warranty obligations	$ 31,995	$ 31,414	$ 29,659	$ 30,547
Recurring \| Warranty obligations for microinverters sold since January 1, 2014 \| Level 3
Product Warranty Liability [Line Items]
Fair value liabilities	$ 11,627	$ 10,332	$ 6,489	$ 6,182

FAIR VALUE MEASUREMENTS - Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Recurring \| Level 3 \| Warranty obligations
Liabilities:
Fair value liabilities	$ 11,627	$ 10,332	$ 6,489	$ 6,182

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 - Warranty obligations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 10,332	$ 6,182
Accruals for warranties issued during period	830	695
Changes in estimates	(266)	(199)
Settlements	(342)	(154)
Increase due to accretion expense	495	384
Other	578	(419)
Balance at end of period	$ 11,627	$ 6,489

FAIR VALUE MEASUREMENTS - Summary of Significant Unobservable Inputs used in the Fair Value Measurement of Liabilities Designated as Level 3 (Details) - Discounted cash flows - Recurring - Level 3 - Warranty obligations for microinverters sold since January 1, 2014	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Profit element and risk premium	17.00%	17.00%
Credit-adjusted risk-free rate	18.00%	19.00%

FAIR VALUE MEASUREMENTS - Narrative (Details) - Discounted cash flows - Recurring - Level 3 - Contingent consideration $ in Millions	3 Months Ended
	Mar. 31, 2017 USD ($)
Derivative [Line Items]
Decrease to fair value measurement as a result of 100 basis point increase	$ 0.5
Increase to fair value measurement as a result of 100 basis point decrease	$ 0.5

GOODWILL AND INTANGIBLE ASSETS - Schedule of Goodwill and Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Goodwill, gross	$ 3,664	$ 3,664
Goodwill	3,664	3,664
Other indefinite-lived intangibles	286	286
Intangible assets with finite lives:
Intangibles assets with finite lives, gross	1,665	1,665
Intangibles assets with finite lives, accumulated amortization	(1,145)	(1,006)
Total	520	659
Patents and licensed technology
Intangible assets with finite lives:
Intangibles assets with finite lives, gross	1,665	1,665
Intangibles assets with finite lives, accumulated amortization	(1,145)	(1,006)
Total	$ 520	$ 659

GOODWILL AND INTANGIBLE ASSETS - Narrative (Details) - USD ($) $ in Millions	1 Months Ended		3 Months Ended
	Oct. 31, 2015	Jul. 31, 2014	Mar. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Amortization expense related to intangible assets			$ 0.1
Patents and licensed technology
Finite-Lived Intangible Assets [Line Items]
Useful life		3 years
ASIC development
Finite-Lived Intangible Assets [Line Items]
Useful life	3 years

GOODWILL AND INTANGIBLE ASSETS - Schedule of Estimated Future Amortization Expense Related to Finite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
2017	$ 416
2018	104
Total	$ 520	$ 659

RESTRUCTURING (Details) - USD ($) $ in Thousands	3 Months Ended
RESTRUCTURING (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Mar. 31, 2016
Restructuring Cost and Reserve [Line Items]
Total restructuring and asset impairment charges	$ 7,200
Restructuring Plan 2016
Restructuring Cost and Reserve [Line Items]
Total restructuring and asset impairment charges	7,247	$ 0
Restructuring Plan 2016 \| Employee severance and benefit arrangements
Restructuring Cost and Reserve [Line Items]
Total restructuring and asset impairment charges	1,592	0
Restructuring Plan 2016 \| Asset impairments
Restructuring Cost and Reserve [Line Items]
Total restructuring and asset impairment charges	522	0
Restructuring Plan 2016 \| Consultants engaged in restructuring activities
Restructuring Cost and Reserve [Line Items]
Total restructuring and asset impairment charges	4,000	0
Restructuring Plan 2016 \| Lease loss reserves and contract termination costs
Restructuring Cost and Reserve [Line Items]
Total restructuring and asset impairment charges	$ 1,133	$ 0

RESTRUCTURING - Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Restructuring Reserve [Roll Forward]
Restructuring charges	$ 7,200
Restructuring Plan 2016
Restructuring Reserve [Roll Forward]
Restructuring reserve, Beginning balance	682
Restructuring charges	7,247	$ 0
Cash payments	(5,871)
Non-cash settlement	(522)
Restructuring reserve, Ending balance	1,536
Employee Severance and Benefits \| Restructuring Plan 2016
Restructuring Reserve [Roll Forward]
Restructuring reserve, Beginning balance	198
Restructuring charges	1,592	0
Cash payments	(1,641)
Non-cash settlement	0
Restructuring reserve, Ending balance	149
Asset Impairments \| Restructuring Plan 2016
Restructuring Reserve [Roll Forward]
Restructuring reserve, Beginning balance	0
Restructuring charges	522	$ 0
Cash payments	0
Non-cash settlement	(522)
Restructuring reserve, Ending balance	0
Lease Loss Reserves and Contractual Obligations \| Restructuring Plan 2016
Restructuring Reserve [Roll Forward]
Restructuring reserve, Beginning balance	484
Restructuring charges	5,133
Cash payments	(4,230)
Restructuring reserve, Ending balance	$ 1,387

DEBT - Narrative (Details)	1 Months Ended		3 Months Ended
DEBT - Narrative (Details)	Feb. 28, 2017 USD ($) $ / shares shares	Jul. 31, 2016 USD ($)	Mar. 31, 2017 USD ($) $ / shares	Mar. 31, 2016 USD ($)	Dec. 18, 2015 USD ($)
Short-term Debt [Line Items]
Proceeds from term loan, net			$ 24,162,000	$ 0
Payments under revolving credit facility			10,100,000	7,000,000
Fair value of warrants issued			1,447,000	$ 0
Tennenbaum Capital Partners, LLC \| Secured Debt
Short-term Debt [Line Items]
Debt instrument face amount		$ 25,000,000.0
Proceeds from term loan, net		$ 25,000,000
Interest rate during period		10.25%
Commitment fee percentage		3.30%
Closing fee (as a percent)		10.00%
Tennenbaum Capital Partners, LLC \| Secured Debt \| Amended Term Loan Agreement, February 2017
Short-term Debt [Line Items]
Debt instrument face amount	$ 25,000,000.0
Tennenbaum Capital Partners, LLC \| Secured Debt \| Minimum
Short-term Debt [Line Items]
Prepayment fee (as a percent)		1.00%
Tennenbaum Capital Partners, LLC \| Secured Debt \| Maximum
Short-term Debt [Line Items]
Prepayment fee (as a percent)		3.00%
Tennenbaum Capital Partners, LLC \| Secured Debt \| LIBOR
Short-term Debt [Line Items]
Interest rate during period		9.5625%
Reduction of interest rate during period (as a percent)		1.00%
Line of Credit \| Wells Fargo Bank \| Revolving Credit Facility
Short-term Debt [Line Items]
Credit line facility			$ 50,000,000.0
Credit line facility, accordion feature					$ 25,000,000.0
Payments under revolving credit facility		$ 10,300,000
Secured Debt \| Tennenbaum Capital Partners, LLC \| Amended Term Loan Agreement, February 2017
Short-term Debt [Line Items]
Interest rate during period	10.3125%
Commitment fee percentage	3.00%
Closing fee (as a percent)	4.00%
Unrestricted cash	$ 10,000,000.0
Number of securities called by warrants (in shares) \| shares	1,220,000
Warrant to purchase common stock, price per share (usd per share) \| $ / shares	$ 1.05
Class of warrant term year	7 years
Secured Debt \| Tennenbaum Capital Partners, LLC \| Term Loan Agreement, July 2016
Short-term Debt [Line Items]
Debt instrument face amount		25,000,000.0
Proceeds from term loan, net		$ 25,000,000
Secured Debt \| Tennenbaum Capital Partners, LLC \| Minimum \| Amended Term Loan Agreement, February 2017
Short-term Debt [Line Items]
Prepayment fee (as a percent)	1.00%
Periodic payments	$ 15,000,000.0
Secured Debt \| Tennenbaum Capital Partners, LLC \| Maximum \| Amended Term Loan Agreement, February 2017
Short-term Debt [Line Items]
Prepayment fee (as a percent)	3.00%
Secured Debt \| Tennenbaum Capital Partners, LLC \| LIBOR \| Amended Term Loan Agreement, February 2017
Short-term Debt [Line Items]
Reduction of interest rate during period (as a percent)	1.00%
Basis spread on variable rate	9.25%
Closing Date to March 31, 2018 \| Secured Debt \| Amended Term Loan Agreement, February 2017
Short-term Debt [Line Items]
Liquidity ratio required	1.5
April 1, 2018 and Thereafter \| Secured Debt \| Amended Term Loan Agreement, February 2017
Short-term Debt [Line Items]
Liquidity ratio required	1.75
Cashless Exercise Warrants
Short-term Debt [Line Items]
Warrant to purchase common stock, price per share (usd per share) \| $ / shares			$ 1.05
Stock price (usd per share) \| $ / shares			$ 1.56
Volatility rate, warrants			85.90%
Risk free interest rate, warrants			2.23%
Dividend rate, warrants			0.00%
Expected term, warrants			7 years

DEBT - Long term debt (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
Term loan	$ 50,000	$ 25,000
Less unamortized discount and issuance costs	(3,119)	(1,200)
Carrying amount of debt	46,881	23,800
Less current portion	(1,497)	(3,032)
Long-term debt	$ 45,384	$ 20,768

DEBT - Maturities (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
2017	$ 0
2018	15,229
2019	20,084
2020	14,687
Total	$ 50,000	$ 25,000

SALE OF COMMON STOCK (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended
SALE OF COMMON STOCK (Details) - USD ($) $ in Thousands	Jan. 31, 2017	Dec. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Subsidiary, Sale of Stock [Line Items]
Proceeds from issuance of common stock			$ 26,522	$ 0
Private Placement
Subsidiary, Sale of Stock [Line Items]
Common stock issued during period (in shares)	10,800,000.0
Gross proceeds from issuance of common stock	$ 10,000
Proceeds from issuance of common stock	$ 10,000
Market Issuance Sales Agreement (ATM)
Subsidiary, Sale of Stock [Line Items]
Common stock issued during period (in shares)			11,100,000
Gross proceeds from issuance of common stock			$ 17,000
Proceeds from issuance of common stock			$ 16,600
Gross aggregate offering price		$ 17,000

STOCK-BASED COMPENSATION - Summary of Stock Option Activity (Details) shares in Thousands	3 Months Ended
	Mar. 31, 2017 $ / shares shares
Number of Shares Outstanding
Outstanding, beginning balance (in shares) \| shares	8,730
Granted (in shares) \| shares	191
Exercised (in shares) \| shares	(6)
Canceled (in shares) \| shares	(812)
Outstanding, ending balance (in shares) \| shares	8,103
Weighted- Average Exercise Price per Share
Outstanding, beginning balance (in usd per share) \| $ / shares	$ 4.56
Granted (in usd per share) \| $ / shares	1.15
Exercised (in usd per share) \| $ / shares	0.42
Canceled (in usd per share) \| $ / shares	6.50
Outstanding, ending balance (in usd per share) \| $ / shares	$ 4.29

STOCK-BASED COMPENSATION - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2017 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of options outstanding	$ 1.3
Total unrecognized compensation cost	$ 7.5
Weighted-average recognition period for unrecognized compensation cost	2 years 4 months 24 days
Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of stock vested during period	$ 0.2
Intrinsic value of restricted stock units outstanding	$ 0.6

STOCK-BASED COMPENSATION - Summary of Restricted Stock Unit Activity (Details) - Restricted stock units shares in Thousands	3 Months Ended
	Mar. 31, 2017 $ / shares shares
RSUs
Outstanding, beginning balance (in shares) \| shares	606
Granted (in shares) \| shares	0
Vested (in shares) \| shares	(146)
Canceled (in shares) \| shares	(40)
Outstanding, ending balance (in shares) \| shares	420
Weighted Average Fair Value per Share at Grant Date
Outstanding, beginning balance (in usd per share) \| $ / shares	$ 9.33
Granted (in usd per share) \| $ / shares
Vested (in usd per share) \| $ / shares	9.21
Canceled (in usd per share) \| $ / shares	11.60
Outstanding, ending balance (in usd per share) \| $ / shares	$ 9.16

STOCK-BASED COMPENSATION - Summary of the Components of Total Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Allocation of Stock-based Compensation Expense Included in the Consolidated Statement of Operations [Abstract]
Total stock-based compensation expense	$ 1,929	$ 2,999
Cost of revenues
Allocation of Stock-based Compensation Expense Included in the Consolidated Statement of Operations [Abstract]
Total stock-based compensation expense	239	307
Research and development
Allocation of Stock-based Compensation Expense Included in the Consolidated Statement of Operations [Abstract]
Total stock-based compensation expense	751	1,127
Sales and marketing
Allocation of Stock-based Compensation Expense Included in the Consolidated Statement of Operations [Abstract]
Total stock-based compensation expense	378	612
General and administrative
Allocation of Stock-based Compensation Expense Included in the Consolidated Statement of Operations [Abstract]
Total stock-based compensation expense	$ 561	$ 953

STOCK-BASED COMPENSATION - Summary of Stock-Based Compensation Associated with Each Type of Award (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 1,929	$ 2,999
Stock options and restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	1,599	2,484
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 330	$ 515

STOCK-BASED COMPENSATION - Summary of the Weighted-Average Grant Date Fair Value of Options Granted (Details) - Stock options - $ / shares	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
The fair value of each option granted during the periods
Weighted average grant date fair value (in usd per share)	$ 0.68	$ 1.28
Expected term (in years)	4 years	4 years 7 months 6 days
Expected volatility	83.60%	77.40%
Annual risk-free rate of return	1.70%	1.20%
Dividend yield	0.00%	0.00%

NET 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
	Mar. 31, 2017	Mar. 31, 2016
Numerator:
Net loss	$ (23,305)	$ (18,795)
Denominator:
Shares used in per share calculation, basic and diluted (in shares)	76,651	46,209
Net loss per share, basic and diluted (in usd per share)	$ (0.30)	$ (0.41)

NET LOSS PER SHARE - Schedule of Potentially Dilutive Securities Excluded from the Computation of Diluted Net Loss Per Share (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
The potential common shares outstanding that were excluded from the computation of diluted net loss per share attributable to common stockholders
Total (in shares)	9,648	9,435
Employee stock options
The potential common shares outstanding that were excluded from the computation of diluted net loss per share attributable to common stockholders
Total (in shares)	8,458	8,160
Restricted stock units
The potential common shares outstanding that were excluded from the computation of diluted net loss per share attributable to common stockholders
Total (in shares)	526	1,164
Warrants to purchase common stock
The potential common shares outstanding that were excluded from the computation of diluted net loss per share attributable to common stockholders
Total (in shares)	664	111