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Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2016	Oct. 31, 2016
Document and Entity Information [Abstract]
Entity Registrant Name	Enphase Energy, Inc.
Entity Central Index Key	0001463101
Document Type	10-Q
Document Period End Date	Sep. 30, 2016
Amendment Flag	false
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q3
Current Fiscal Year End	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		61,909,348

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 24,112	$ 28,452
Accounts receivable, net of allowances of $5,002 and $1,808 at September 30, 2016 and December 31, 2015, respectively	59,482	46,099
Inventory	39,101	40,800
Prepaid expenses and other assets	7,187	6,417
Total current assets	129,882	121,768
Property and equipment, net	32,453	32,118
Goodwill	3,745	3,745
Intangibles, net	1,669	2,220
Other assets	8,679	5,677
Total assets	176,428	165,528
Current liabilities:
Accounts payable	32,551	25,569
Accrued liabilities	26,667	19,292
Deferred revenues, current	5,942	3,915
Warranty obligations, current (includes $3,500 and $2,601 measured at fair value at September 30, 2016 and December 31, 2015, respectively)	6,761	7,072
Revolving credit facility	12,450	17,000
Current portion of term loan	1,197	0
Total current liabilities	85,568	72,848
Long-term liabilities:
Deferred revenues, noncurrent	31,827	25,115
Warranty obligations, noncurrent (includes $6,015 and $3,581 measured at fair value at September 30, 2016 and December 31, 2015, respectively)	23,588	23,475
Other liabilities	2,408	2,641
Term loan, less current portion	22,808	0
Total liabilities	166,199	124,079
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; 59,958 and 45,821 shares issued and outstanding at September 30, 2016 and December 31, 2015, respectively	1	0
Additional paid-in capital	247,829	224,732
Accumulated deficit	(237,347)	(183,073)
Accumulated other comprehensive loss	(254)	(210)
Total stockholders’ equity	10,229	41,449
Total liabilities and stockholders’ equity	$ 176,428	$ 165,528

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Allowances, accounts receivable	$ 5,002	$ 1,808
Warranty obligations, current at fair value	3,500	2,601
Warranty obligations, non-current at fair value	$ 6,015	$ 3,581
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
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)	59,958,000	45,821,000
Common stock, shares outstanding (in shares)	59,958,000	45,821,000

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Statement [Abstract]
Net revenues	$ 88,684	$ 102,874	$ 231,990	$ 291,620
Cost of revenues	72,805	71,408	190,215	199,103
Gross profit	15,879	31,466	41,775	92,517
Operating expenses:
Research and development	13,169	12,059	39,326	38,275
Sales and marketing	11,016	10,510	31,218	34,955
General and administrative	6,708	7,118	21,121	23,425
Restructuring charges	2,717	0	2,717	0
Total operating expenses	33,610	29,687	94,382	96,655
Income (loss) from operations	(17,731)	1,779	(52,607)	(4,138)
Other income (expense), net:
Interest expense	(1,234)	(140)	(1,598)	(305)
Other income (expense)	353	(704)	655	(1,152)
Total other expense, net	(881)	(844)	(943)	(1,457)
Income (loss) before income taxes	(18,612)	935	(53,550)	(5,595)
Provision for income taxes	(144)	(311)	(724)	(704)
Net income (loss)	$ (18,756)	$ 624	$ (54,274)	$ (6,299)
Net loss per share, basic and diluted (in usd per share)	$ (0.40)	$ 0.01	$ (1.16)	$ (0.14)
Shares used in per share calculation, basic	47,278	44,734	46,704	44,339
Shares used in per share calculation, diluted	47,278	47,996	46,704	44,339

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (18,756)	$ 624	$ (54,274)	$ (6,299)
Other comprehensive income (loss):
Foreign currency translation adjustments	54	187	(44)	(132)
Comprehensive income (loss)	$ (18,702)	$ 811	$ (54,318)	$ (6,431)

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net loss	$ (54,274)	$ (6,299)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	8,039	7,704
Provision for doubtful accounts	3,194	344
Asset impairment charges	1,440	479
Amortization of debt issuance costs	101	120
Stock-based compensation	8,239	9,579
Revaluation of contingent consideration liability	0	(1,600)
Changes in operating assets and liabilities:
Accounts receivable	(16,577)	(30,547)
Inventory	1,699	(15,127)
Prepaid expenses and other assets	(3,857)	(5,008)
Accounts payable, accrued and other liabilities	14,867	5,004
Warranty obligations	(198)	(1,134)
Deferred revenues	8,739	7,176
Net cash used in operating activities	(28,588)	(29,309)
Cash flows from investing activities:
Purchases of property and equipment	(9,607)	(9,682)
Purchases of intangible assets	(678)	0
Net cash used in investing activities	(10,285)	(9,682)
Cash flows from financing activities:
Proceeds from public offering of common stock, net of underwriting fees	14,593	0
Proceeds from term loan	24,175	0
Proceeds from borrowings under revolving credit facility	10,000	34,000
Payments under revolving credit facility	(14,550)	(17,000)
Payments for debt issuance costs and offering costs	(401)	0
Contingent consideration payment related to prior acquisition	(29)	0
Proceeds from issuance of common stock under employee stock plans	852	2,866
Net cash provided by financing activities	34,640	19,866
Effect of exchange rate changes on cash	(107)	(416)
Net decrease in cash and cash equivalents	(4,340)	(19,541)
Cash and cash equivalents—Beginning of period	28,452	42,032
Cash and cash equivalents—End of period	24,112	22,491
Supplemental disclosures of non-cash investing and financing activities:
Purchases of fixed and intangible assets included in accounts payable	517	584
Deferred public offering costs included in accounts payable	$ 446	$ 0

DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION	9 Months Ended
DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION	Sep. 30, 2016
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 over 12.6 million microinverters representing over 3 gigawatts of solar PV generating capacity, and more than 540,000 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. 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 and nine months ended September 30, 2016 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, 2015. There have been no material changes in the Company’s significant accounting policies during the nine months ended September 30, 2016, as compared to the significant accounting policies described in the Company’s Annual Report on Form 10-K for the year ended December 31, 2015. 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 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 August 2014, the FASB issued ASU 2014-15, “Presentation of Financial Statements—Going Concern.” The update provides U.S. GAAP guidance on management’s responsibility in evaluating whether there is substantial doubt about a company’s ability to continue as a going concern and about related footnote disclosures. For each reporting period, management will be required to evaluate whether there are conditions or events that raise substantial doubt about a company’s ability to continue as a going concern within one year from the date the financial statements are issued. The amendments in this update are effective for the annual period ending after December 15, 2016 and for annual and interim periods thereafter. The Company is currently evaluating the impact of adoption on the consolidated financial statements. 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. Early adoption is permitted for any interim and annual financial statements that have not yet been issued. The Company 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. 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 Company is currently evaluating the impact of adoption on the consolidated financial statements.

INVENTORY

9 Months Ended

Sep. 30, 2016

Inventory Disclosure [Abstract]

INVENTORY

Inventory as of September 30, 2016 and December 31, 2015 consists of the following (in thousands):



	September 30, 2016		December 31, 2015
Raw materials	$	4,677	$	2,202
Finished goods	34,424		38,598
Total inventory	$	39,101	$	40,800

WARRANTY OBLIGATIONS

9 Months Ended

Sep. 30, 2016

Product Warranties Disclosures [Abstract]

WARRANTY OBLIGATIONS

The Company’s warranty activities during the three and nine months ended September 30, 2016 and 2015 were as follows (in thousands):



	Three Months Ended September 30,						Nine Months Ended September 30,
	2016			2015			2016			2015
Warranty obligations, beginning of period	$	30,066		$	33,763		$	30,547		$	33,940
Accruals for warranties issued during period	1,194			1,400			2,931			3,707
Changes in estimates	783			498			1,548			736
Settlements	(2,561		)	(2,615		)	(6,517		)	(5,480		)
Increase due to accretion expense	461			272			1,279			643
Other	406			(512		)	561			(740		)
Warranty obligations, end of period	$	30,349		$	32,806		$	30,349		$	32,806
Less current portion							$	(6,761	)	$	(6,612	)
Noncurrent							$	23,588		$	26,194

As of September 30, 2016, the $30.3 million of warranty obligations included $9.5 million measured at fair value. As of December 31, 2015, the $30.5 million of warranty obligations included $6.2 million measured at fair value. See Note 4, “Fair Value Measurements” for additional information.

FAIR VALUE MEASUREMENTS

9 Months Ended

Sep. 30, 2016

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 assets and liabilities that were measured at fair value on a recurring basis and its categorization within the fair value hierarchy at September 30, 2016 and December 31, 2015 (in thousands):



	Fair Value Hierarchy	September 30, 2016		December 31, 2015
Assets:
Foreign currency forward contracts	Level 2	$	—	$	86

Liabilities:
Foreign currency forward contracts	Level 2	$	—	$	9
Warranty obligations	Level 3	9,515		6,182
Contingent consideration	Level 3	444		473

Derivative Instruments

The Company utilizes foreign currency forward contracts from time to time to reduce the impact of foreign currency fluctuations arising from both sales and purchases denominated in Euros and the British Pound Sterling. At September 30, 2016, the Company did not have any outstanding foreign currency forward contracts. At December 31, 2015, the notional amount of the Company’s foreign currency forward contracts outstanding was $2.4 million. For the three and nine months ended September 30, 2016 and 2015, gains and losses from foreign currency forward contracts recorded in other income (expense), net were insignificant.

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 September 30,						Nine Months Ended September 30,
	2016			2015			2016			2015
Balance at beginning of period	$	8,053		$	5,803		$	6,182		$	3,562
Accruals for warranties issued during period	1,185			1,327			2,898			3,510
Changes in estimates	(200		)	—			(678		)	—
Settlements	(390		)	(74		)	(726		)	(159		)
Increase due to accretion expense	461			272			1,279			643
Other	406			(512		)	560			(740		)
Balance at end of period	$	9,515		$	6,816		$	9,515		$	6,816

Contingent Consideration Liability

The following table provides information regarding changes in financial liabilities related to the contingent consideration liability arising from a previous acquisition measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the periods indicated (in thousands):



	Three Months Ended September 30,					Nine Months Ended September 30,
	2016		2015			2016			2015
Balance at beginning of period	$	444	$	1,400		$	473		$	2,300
Revaluations	—		(700		)	—			(1,600		)
Contingent consideration payment	—		—			(29		)	—
Balance at end of period	$	444	$	700		$	444		$	700

Quantitative and Qualitative Information about Level 3 Fair Value Measurements

As of September 30, 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	21%

Contingent consideration liability	Probability-weighted discounted cash flows	Risk-adjusted discount rate	17%

As of December 31, 2015, 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	25%

Contingent consideration liability	Probability-weighted discounted cash flows	Risk-adjusted discount rate	17%

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 $0.3 million reduction of the liability. Decreasing the discount rate by 100 basis points would result in a $0.3 million increase to the liability.

Contingent Consideration Liability

Changes in assumed probability adjustments with respect to achievement of target metrics can materially impact the fair value measurement of contingent consideration as of the acquisition date and for each subsequent period. Assumptions about the probability and amount of payout require less subjectivity over the course of the earnout period as management refines estimates based on actual events. Due to the short duration of the remaining earnout period, increasing or decreasing the risk-adjusted discount rate by 100 basis points would not have a material impact on the fair value measurement of the contingent consideration 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

9 Months Ended

Sep. 30, 2016

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 September 30, 2016 and December 31, 2015 (in thousands):



	September 30, 2016							December 31, 2015
	Gross		Accumulated Amortization			Net		Gross		Accumulated Amortization			Net
Goodwill	$	3,745	$	—		$	3,745	$	3,745	$	—		$	3,745

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

Intangible assets with finite lives:
Customer relationships	$	900	$	(315	)	$	585	$	900	$	(180	)	$	720
Patents and licensed technology	1,665		(867		)	798		1,665		(451		)	1,214
Total	$	2,565	$	(1,182	)	$	1,383	$	2,565	$	(631	)	$	1,934

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. The customer relationship intangible asset associated with a prior acquisition is being amortized on a straight-line basis over its estimated useful life of 5 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 nine months ended September 30, 2016, amortization expense related to intangible assets was $0.6 million. As of September 30, 2016, estimated future amortization expense related to finite-lived intangible assets was as follows:



Year	(In thousands)
2016	$	184
2017	610
2018	409
2019	180
Total	$	1,383

- 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 AND ASSET IMPAIRMENT CHARGES (Notes)

9 Months Ended

Sep. 30, 2016

Restructuring and Related Activities [Abstract]

RESTRUCTURING AND ASSET IMPAIRMENT CHARGES

RESTRUCTURING

In the third quarter of 2016, the Company implemented a restructuring plan to lower its operating expenses. The restructuring plan led to a reduction of its workforce globally by approximately 11% of total headcount throughout all areas of the organization and an elimination of certain non-core projects. The restructuring actions are expected to be completed by the end of the fourth quarter of 2016.

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



	Three Months Ended September 30,
	2016		2015
Employee severance and benefit arrangements	$	1,308	$	—
Asset impairments	1,409		—
Total restructuring and asset impairment charges	$	2,717	$	—

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			Total
Balance at beginning of period as of December 31, 2015	$	—		$	—		$	—
Charges	1,308			1,409			2,717
Cash payments	(85		)	—			(85		)
Non-cash settlement	—			(1,409		)	(1,409		)
Balance at end of period as of September 30, 2016	$	1,223		$	—		$	1,223

DEBT

9 Months Ended

Sep. 30, 2016

Short-term Debt [Abstract]

DEBT

Revolving Credit Facility

The Company maintains 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.

Availability under the Revolver is subject to a borrowing base calculation that limits availability to a percentage of eligible domestic accounts receivable plus a percentage of the value of eligible domestic inventory, less certain reserves. Borrowings under the Revolver bear interest in cash at an annual rate equal to, at the Company’s option, either LIBOR or a “base rate” that is comprised of, among other things, the prime rate, plus a margin that is between 1.0% and 3.75% depending on the currency borrowed and the specific term of repayment. The Revolver requires the Company to pay an unused line fee between 0.25% and 0.375% based on the average daily unused portion of the revolving credit commitment.

The Revolver is secured by a first-priority security interest on substantially all assets of the Company other than intellectual property and contains customary affirmative and negative covenants (including restrictions on the Company’s ability to make dividend payments) and events of default. In addition, the Revolver requires the Company to maintain at least $15.0 million of liquidity at all times, consisting of cash on hand and undrawn availability under the Revolver (defined as borrowing base less outstanding borrowings under the Revolver) of at least $5.0 million. In July 2016, the Company entered into an amendment to the Revolver with Wells Fargo. The amendment, among other things, allowed the Company to incur indebtedness related to a term loan (described below} and increased the amount of undrawn availability that must be maintained as part of the Revolver’s $15.0 million minimum liquidity covenant from $5.0 million to $12.5 million. The Company was in compliance with such covenants as of September 30, 2016.

As of September 30, 2016, outstanding borrowings under the Revolver were $12.5 million. Based upon its eligible borrowing base, net of the restrictions concerning minimum liquidity requirement, the Company could have borrowed an additional $8.8 million. The weighted-average interest rate related to the outstanding balance was 5.0%.

Term Loan

In July 2016, the Company entered into a Term Loan Agreement with lenders that are affiliates of Tennenbaum Capital Partners, LLC. 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 are interest only, followed by consecutive equal monthly payments of principal plus accrued interest beginning on July 1, 2017 and continuing 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 we achieve 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. We 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.

The term loan is secured by a second-priority security interest on substantially all our assets except intellectual property. The Term Loan Agreement does not contain any financial covenants, but is subject to customary affirmative and negative covenants including restrictions on creation of liens, dispositions of assets, dividends, mergers, or changing the nature of the Company’s business; in each case, subject to certain customary exceptions. In addition, the Term Loan Agreement 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.

Long-term debt was comprised of the following at September 30, 2016 and December 31, 2015 (in thousands):



	September 30, 2016			December 31, 2015
Term loan	$	25,000		$	—
Less unamortized discount and issuance costs	(995		)	—
Carrying amount of debt	24,005			—
Less current portion	(1,197		)	—
Long-term debt	$	22,808		$	—

As of September 30, 2016, the amount of scheduled principal payments due on the term loan is as follows (in thousands):



Year	Amounts
2016	$	—
2017	3,032
2018	7,824
2019	8,665
2020	5,479
Total	$	25,000

COMMITMENTS AND CONTINGENCIES	9 Months Ended
COMMITMENTS AND CONTINGENCIES	Sep. 30, 2016
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. The Company believes its cash on hand of $24.1 million as of September 30, 2016, its reduced cost structure as a result of its restructuring initiatives implemented in the third quarter of 2016, together with borrowings expected to be available under the Revolver, will be sufficient to fund its operations and satisfy its working capital needs, capital asset purchases, indebtedness payments and outstanding commitments for at least the next 12 months. If the Company is unable to meet its projected performance targets or manage its inventory levels to align with anticipated demand, its liquidity could be adversely impacted and it may need to seek additional sources of liquidity. If additional sources of liquidity are needed, the Company may consider new debt or equity offerings, but there is no assurance that such transactions could be consummated on acceptable terms or at all. Failure to raise sufficient capital when needed could have a material adverse effect on its business, results of operations and financial position.

SALE OF COMMON STOCK	9 Months Ended
SALE OF COMMON STOCK	Sep. 30, 2016
Equity [Abstract]
SALE OF COMMON STOCK	SALE OF COMMON STOCK On September 28, 2016, the Company completed a public offering of 13,000,000 shares of its common stock at a price to the public of $1.20 per share. Net proceeds realized were approximately $14.0 million after deducting underwriting fees and estimated offering costs. The Company intends to use the net proceeds for working capital and general corporate purposes. On October 11, 2016, the underwriter for the offering exercised in full an over-allotment option to purchase an additional 1,950,000 shares of the Company’s common stock, which generated additional net proceeds of approximately $2.2 million. The sale of the additional shares occurred subsequent to the quarter ended September 30, 2016, and the effect of the sale is not reflected in these condensed consolidated financial statements.

- 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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
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-Section S99
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-Section S99
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
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Reference 8: http://www.xbrl.org/2003/role/presentationRef
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
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Reference 12: http://www.xbrl.org/2003/role/presentationRef
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Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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+ Details

STOCK-BASED COMPENSATION

9 Months Ended

Sep. 30, 2016

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, 2015.

Equity Awards Activity

Stock Options

The following is a summary of stock option activity for the nine months ended September 30, 2016 (in thousands, except per share data):



	Number of Shares Outstanding		Weighted- Average Exercise Price per Share
Outstanding at December 31, 2015	8,173		$	5.36
Granted	2,367		2.15
Exercised	(374	)	0.39
Canceled	(831	)	7.01
Outstanding at September 30, 2016	9,335		4.60

The intrinsic value of options exercised in the nine months ended September 30, 2016 was $0.7 million. As of September 30, 2016, the intrinsic value of options outstanding was $1.1 million based on the closing price of the Company’s stock as of September 30, 2016.

Restricted Stock Units

The following is a summary of restricted stock unit activity for the nine months ended September 30, 2016 (in thousands, except per share data):



	RSUs		Weighted Average Fair Value per Share at Grant Date
Outstanding at December 31, 2015	1,313		$	9.31
Granted	54		1.99
Vested	(432	)	9.13
Canceled	(206	)	7.41
Outstanding at September 30, 2016	729		9.41

The total intrinsic value of restricted stock units that were vested in the nine months ended September 30, 2016 was $0.8 million. As of September 30, 2016, the intrinsic value of restricted stock units outstanding was $0.9 million based on the closing price of the Company’s stock as of September 30, 2016.

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 September 30,				Nine Months Ended September 30,
	2016		2015		2016		2015
Cost of revenues	$	295	$	331	$	907	$	913
Research and development	941		1,141		3,047		3,379
Sales and marketing	560		803		1,760		2,510
General and administrative	736		1,008		2,525		2,777
Total	$	2,532	$	3,283	$	8,239	$	9,579

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



	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2015		2016		2015
Stock options and restricted stock units	$	1,983	$	2,753	$	6,703	$	8,153
Employee stock purchase plan	549		530		1,536		1,426
Total	$	2,532	$	3,283	$	8,239	$	9,579

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 September 30,						Nine Months Ended September 30,
	2016			2015			2016			2015
Weighted average grant date fair value	$	1.25		$	3.01		$	1.31		$	5.40
Expected term (in years)	4.5			4.6			4.5			4.5
Expected volatility	84.7		%	72.2		%	79.8		%	72.1		%
Annual risk-free rate of return	1.1		%	1.5		%	1.1		%	1.4		%
Dividend yield	0.0		%	0.0		%	0.0		%	0.0		%

As of September 30, 2016, there was approximately $12.5 million of total unrecognized compensation expense related to unvested equity awards expected to be recognized over a weighted-average period of 2.3 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	9 Months Ended
INCOME TAXES	Sep. 30, 2016
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The Company used the discrete tax approach in calculating the tax expense for the three and nine months ended September 30, 2016 and 2015 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. Under Accounting Standards Codification 740, “Income Taxes,” a provision for income taxes must be provided on the undistributed earnings of foreign subsidiaries unless such earnings are deemed to be permanently reinvested outside the United States. Prior to 2016, the Company did not provide for U.S. tax on foreign unremitted earnings because the Company considered such earnings to be permanently reinvested outside the U.S. During the nine months ended September 30, 2016, due to recent developments in its business, the Company determined that subsidiaries with cumulative earnings were not deemed to be permanently invested. Accordingly, the Company recorded income tax expense of $0.1 million on cumulative foreign earnings of approximately $4.5 million that the Company determined no longer met the criteria to be considered permanently invested.

NET INCOME (LOSS) PER SHARE

9 Months Ended

Sep. 30, 2016

Earnings Per Share [Abstract]

NET INCOME (LOSS) PER SHARE

Basic net income (loss) per share is computed by dividing net income (loss) by the weighted average number of shares of common stock outstanding during the period. Diluted 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 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 income (loss) per share.

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



	Three Months Ended September 30,					Nine Months Ended September 30,
	2016			2015		2016			2015
Numerator:
Net income (loss)	$	(18,756	)	$	624	$	(54,274	)	$	(6,299	)

Denominator:
Weighted average common shares outstanding	47,278			44,734		46,704			44,339
Effect of dilutive securities
Employee stock-based awards	—			3,261		—			—
Warrants	—			1		—			—
Weighted average common shares outstanding for diluted calculation	47,278			47,996		46,704			44,339

Net income (loss) per share, basic	$	(0.40	)	$	0.01	$	(1.16	)	$	(0.14	)
Net income (loss) per share, diluted	$	(0.40	)	$	0.01	$	(1.16	)	$	(0.14	)

For the three months ended September 30, 2015, the Company excluded 6.3 million of potential common shares outstanding from the calculation of diluted net income per share because their effect would have been antidilutive. In periods of net loss, all potential common shares were excluded from the diluted calculation because their effect would have been antidilutive. The following table summarizes the potential common shares excluded from the diluted calculation for the periods indicated (in thousands):



	Three Months Ended September 30,		Nine Months Ended September 30,
	2016	2015	2016	2015
Employee stock options	9,383	4,817	8,944	8,718
Restricted stock units	840	1,523	994	1,551
Warrants to purchase common stock	45	—	85	111
Total	10,268	6,340	10,023	10,380

DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION (Policies)	9 Months Ended
	Sep. 30, 2016
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 and nine months ended September 30, 2016 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, 2015.
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 Issued Accounting Pronouncements Not Yet Effective	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 August 2014, the FASB issued ASU 2014-15, “Presentation of Financial Statements—Going Concern.” The update provides U.S. GAAP guidance on management’s responsibility in evaluating whether there is substantial doubt about a company’s ability to continue as a going concern and about related footnote disclosures. For each reporting period, management will be required to evaluate whether there are conditions or events that raise substantial doubt about a company’s ability to continue as a going concern within one year from the date the financial statements are issued. The amendments in this update are effective for the annual period ending after December 15, 2016 and for annual and interim periods thereafter. The Company is currently evaluating the impact of adoption on the consolidated financial statements. 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. Early adoption is permitted for any interim and annual financial statements that have not yet been issued. The Company 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. 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 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 and nine months ended September 30, 2016 and 2015 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)

9 Months Ended

Sep. 30, 2016

Inventory Disclosure [Abstract]

Summary of Inventory

Inventory as of September 30, 2016 and December 31, 2015 consists of the following (in thousands):



	September 30, 2016		December 31, 2015
Raw materials	$	4,677	$	2,202
Finished goods	34,424		38,598
Total inventory	$	39,101	$	40,800

WARRANTY OBLIGATIONS (Tables)

9 Months Ended

Sep. 30, 2016

Product Warranties Disclosures [Abstract]

Summary of Warranty Activities

The Company’s warranty activities during the three and nine months ended September 30, 2016 and 2015 were as follows (in thousands):



	Three Months Ended September 30,						Nine Months Ended September 30,
	2016			2015			2016			2015
Warranty obligations, beginning of period	$	30,066		$	33,763		$	30,547		$	33,940
Accruals for warranties issued during period	1,194			1,400			2,931			3,707
Changes in estimates	783			498			1,548			736
Settlements	(2,561		)	(2,615		)	(6,517		)	(5,480		)
Increase due to accretion expense	461			272			1,279			643
Other	406			(512		)	561			(740		)
Warranty obligations, end of period	$	30,349		$	32,806		$	30,349		$	32,806
Less current portion							$	(6,761	)	$	(6,612	)
Noncurrent							$	23,588		$	26,194

FAIR VALUE MEASUREMENTS (Tables)

9 Months Ended

Sep. 30, 2016

Fair Value Disclosures [Abstract]

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



	Fair Value Hierarchy	September 30, 2016		December 31, 2015
Assets:
Foreign currency forward contracts	Level 2	$	—	$	86

Liabilities:
Foreign currency forward contracts	Level 2	$	—	$	9
Warranty obligations	Level 3	9,515		6,182
Contingent consideration	Level 3	444		473

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 September 30,						Nine Months Ended September 30,
	2016			2015			2016			2015
Balance at beginning of period	$	8,053		$	5,803		$	6,182		$	3,562
Accruals for warranties issued during period	1,185			1,327			2,898			3,510
Changes in estimates	(200		)	—			(678		)	—
Settlements	(390		)	(74		)	(726		)	(159		)
Increase due to accretion expense	461			272			1,279			643
Other	406			(512		)	560			(740		)
Balance at end of period	$	9,515		$	6,816		$	9,515		$	6,816

Summary of Changes in Financial Liabilities Related to Contingent Consideration Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs



	Three Months Ended September 30,					Nine Months Ended September 30,
	2016		2015			2016			2015
Balance at beginning of period	$	444	$	1,400		$	473		$	2,300
Revaluations	—		(700		)	—			(1,600		)
Contingent consideration payment	—		—			(29		)	—
Balance at end of period	$	444	$	700		$	444		$	700

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

As of September 30, 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	21%

Contingent consideration liability	Probability-weighted discounted cash flows	Risk-adjusted discount rate	17%

As of December 31, 2015, 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	25%

Contingent consideration liability	Probability-weighted discounted cash flows	Risk-adjusted discount rate	17%

GOODWILL AND INTANGIBLE ASSETS (Tables)

9 Months Ended

Sep. 30, 2016

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 September 30, 2016 and December 31, 2015 (in thousands):



	September 30, 2016							December 31, 2015
	Gross		Accumulated Amortization			Net		Gross		Accumulated Amortization			Net
Goodwill	$	3,745	$	—		$	3,745	$	3,745	$	—		$	3,745

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

Intangible assets with finite lives:
Customer relationships	$	900	$	(315	)	$	585	$	900	$	(180	)	$	720
Patents and licensed technology	1,665		(867		)	798		1,665		(451		)	1,214
Total	$	2,565	$	(1,182	)	$	1,383	$	2,565	$	(631	)	$	1,934

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



Year	(In thousands)
2016	$	184
2017	610
2018	409
2019	180
Total	$	1,383

RESTRUCTURING AND ASSET IMPAIRMENT CHARGES (Tables)

9 Months Ended

Sep. 30, 2016

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 September 30,
	2016		2015
Employee severance and benefit arrangements	$	1,308	$	—
Asset impairments	1,409		—
Total restructuring and asset impairment charges	$	2,717	$	—

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			Total
Balance at beginning of period as of December 31, 2015	$	—		$	—		$	—
Charges	1,308			1,409			2,717
Cash payments	(85		)	—			(85		)
Non-cash settlement	—			(1,409		)	(1,409		)
Balance at end of period as of September 30, 2016	$	1,223		$	—		$	1,223

DEBT - (Tables)

9 Months Ended

Sep. 30, 2016

Debt Disclosure [Abstract]

Schedule of Debt

Long-term debt was comprised of the following at September 30, 2016 and December 31, 2015 (in thousands):



	September 30, 2016			December 31, 2015
Term loan	$	25,000		$	—
Less unamortized discount and issuance costs	(995		)	—
Carrying amount of debt	24,005			—
Less current portion	(1,197		)	—
Long-term debt	$	22,808		$	—

Schedule of Maturities of Long-term Debt

As of September 30, 2016, the amount of scheduled principal payments due on the term loan is as follows (in thousands):



Year	Amounts
2016	$	—
2017	3,032
2018	7,824
2019	8,665
2020	5,479
Total	$	25,000

STOCK-BASED COMPENSATION (Tables)

9 Months Ended

Sep. 30, 2016

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 nine months ended September 30, 2016 (in thousands, except per share data):



	Number of Shares Outstanding		Weighted- Average Exercise Price per Share
Outstanding at December 31, 2015	8,173		$	5.36
Granted	2,367		2.15
Exercised	(374	)	0.39
Canceled	(831	)	7.01
Outstanding at September 30, 2016	9,335		4.60

Summary of Restricted Stock Unit Activity

The following is a summary of restricted stock unit activity for the nine months ended September 30, 2016 (in thousands, except per share data):



	RSUs		Weighted Average Fair Value per Share at Grant Date
Outstanding at December 31, 2015	1,313		$	9.31
Granted	54		1.99
Vested	(432	)	9.13
Canceled	(206	)	7.41
Outstanding at September 30, 2016	729		9.41

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 September 30,				Nine Months Ended September 30,
	2016		2015		2016		2015
Cost of revenues	$	295	$	331	$	907	$	913
Research and development	941		1,141		3,047		3,379
Sales and marketing	560		803		1,760		2,510
General and administrative	736		1,008		2,525		2,777
Total	$	2,532	$	3,283	$	8,239	$	9,579

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 September 30,				Nine Months Ended September 30,
	2016		2015		2016		2015
Stock options and restricted stock units	$	1,983	$	2,753	$	6,703	$	8,153
Employee stock purchase plan	549		530		1,536		1,426
Total	$	2,532	$	3,283	$	8,239	$	9,579

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



	Three Months Ended September 30,						Nine Months Ended September 30,
	2016			2015			2016			2015
Weighted average grant date fair value	$	1.25		$	3.01		$	1.31		$	5.40
Expected term (in years)	4.5			4.6			4.5			4.5
Expected volatility	84.7		%	72.2		%	79.8		%	72.1		%
Annual risk-free rate of return	1.1		%	1.5		%	1.1		%	1.4		%
Dividend yield	0.0		%	0.0		%	0.0		%	0.0		%

NET INCOME (LOSS) PER SHARE (Tables)

9 Months Ended

Sep. 30, 2016

Earnings Per Share [Abstract]

Schedule of Computation of Basic and Diluted Net Loss Per Share

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



	Three Months Ended September 30,					Nine Months Ended September 30,
	2016			2015		2016			2015
Numerator:
Net income (loss)	$	(18,756	)	$	624	$	(54,274	)	$	(6,299	)

Denominator:
Weighted average common shares outstanding	47,278			44,734		46,704			44,339
Effect of dilutive securities
Employee stock-based awards	—			3,261		—			—
Warrants	—			1		—			—
Weighted average common shares outstanding for diluted calculation	47,278			47,996		46,704			44,339

Net income (loss) per share, basic	$	(0.40	)	$	0.01	$	(1.16	)	$	(0.14	)
Net income (loss) per share, diluted	$	(0.40	)	$	0.01	$	(1.16	)	$	(0.14	)

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

The following table summarizes the potential common shares excluded from the diluted calculation for the periods indicated (in thousands):



	Three Months Ended September 30,		Nine Months Ended September 30,
	2016	2015	2016	2015
Employee stock options	9,383	4,817	8,944	8,718
Restricted stock units	840	1,523	994	1,551
Warrants to purchase common stock	45	—	85	111
Total	10,268	6,340	10,023	10,380

DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION (Details) system in Thousands, microinverter in Millions, watt in Billions	Sep. 30, 2016 system country watt microinverter
Microinverter [Member]
Product Information [Line Items]
Number of product shipped \| microinverter	12.6
Number of watts \| watt	3
Residential And Commercial Systems [Member]
Product Information [Line Items]
Number of product deployed \| system	540
Number of countries in which product is deployed \| country	100

INVENTORY - Summary of Inventory (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Schedule of inventory
Raw materials	$ 4,677	$ 2,202
Finished goods	34,424	38,598
Total inventory	$ 39,101	$ 40,800

WARRANTY OBLIGATIONS - Summary of Warranty Activities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Changes in the Company's product warranty liability
Warranty obligations, beginning of period	$ 30,066	$ 33,763	$ 30,500	$ 33,940
Accruals for warranties issued during period	1,194	1,400	2,931	3,707
Changes in estimates	783	498	1,548	736
Settlements	(2,561)	(2,615)	(6,517)	(5,480)
Increase due to accretion expense	461	272	1,279	643
Other	406	(512)	561	(740)
Warranty obligations, end of period	30,349	32,806	30,349	32,806
Less current portion	(6,761)	(6,612)	(6,761)	(6,612)	$ (7,072)
Noncurrent	$ 23,588	$ 26,194	$ 23,588	$ 26,194	$ 23,475

WARRANTY OBLIGATIONS - Narrative (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Product Warranty Liability [Line Items]
Warranty obligations, end of period	$ 30,349	$ 30,066	$ 30,500	$ 32,806	$ 33,763	$ 33,940
Recurring \| Warranty obligations for microinverters sold since January 1, 2014 \| Level 3
Product Warranty Liability [Line Items]
Fair value liabilities	$ 9,515	$ 8,053	$ 6,182	$ 6,816	$ 5,803	$ 3,562

FAIR VALUE MEASUREMENTS - Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Recurring - USD ($) $ in Thousands	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Level 2
Assets:
Foreign currency forward contracts	$ 0		$ 86
Liabilities:
Foreign currency forward contracts	0		9
Level 3 \| Warranty obligations
Liabilities:
Fair value liabilities	9,515	$ 8,053	6,182	$ 6,816	$ 5,803	$ 3,562
Level 3 \| Contingent consideration
Liabilities:
Fair value liabilities	$ 444		$ 473

FAIR VALUE MEASUREMENTS - Narrative (Details) - USD ($)	9 Months Ended
FAIR VALUE MEASUREMENTS - Narrative (Details) - USD ($)	Sep. 30, 2016	Dec. 31, 2015
Discounted cash flows \| Recurring \| Level 3 \| Contingent consideration
Derivative [Line Items]
Decrease to fair value measurement as a result of 100 basis point increase	$ 300,000
Increase to fair value measurement as a result of 100 basis point decrease	300,000
Not designated as hedging instrument \| Foreign exchange forward
Derivative [Line Items]
Notional amount of foreign currency	$ 0	$ 2,400,000

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		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 8,053	$ 5,803	$ 6,182	$ 3,562
Accruals for warranties issued during period	1,185	1,327	2,898	3,510
Changes in estimates	(200)	0	(678)	0
Settlements	(390)	(74)	(726)	(159)
Increase due to accretion expense	461	272	1,279	643
Other	406	(512)	560	(740)
Balance at end of period	$ 9,515	$ 6,816	$ 9,515	$ 6,816

FAIR VALUE MEASUREMENTS - Summary of Changes in Financial Liabilities Related to Contingent Consideration Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Details) - Next Phase Solar, Inc. - Contingent consideration - Recurring - Level 3 - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 444	$ 1,400	$ 473	$ 2,300
Revaluations	0	(700)	0	(1,600)
Contingent consideration payment	0	0	(29)	0
Balance at end of period	$ 444	$ 700	$ 444	$ 700

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	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Warranty obligations for microinverters sold since January 1, 2014
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Profit element and risk premium	17.00%	17.00%
Credit-adjusted risk-free rate	21.00%	25.00%
Contingent consideration liability
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Risk-adjusted discount rate	17.00%	17.00%

GOODWILL AND INTANGIBLE ASSETS - Schedule of Goodwill and Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Goodwill, gross	$ 3,745	$ 3,745
Goodwill	3,745	3,745
Other indefinite-lived intangibles	286	286
Intangible assets with finite lives:
Intangibles assets with finite lives, gross	2,565	2,565
Intangibles assets with finite lives, accumulated amortization	(1,182)	(631)
Total	1,383	1,934
Customer relationships
Intangible assets with finite lives:
Intangibles assets with finite lives, gross	900	900
Intangibles assets with finite lives, accumulated amortization	(315)	(180)
Total	585	720
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	(867)	(451)
Total	$ 798	$ 1,214

GOODWILL AND INTANGIBLE ASSETS - Narrative (Details) - USD ($) $ in Millions	1 Months Ended			9 Months Ended
	Oct. 31, 2015	Dec. 31, 2014	Jul. 31, 2014	Sep. 30, 2016
Finite-Lived Intangible Assets [Line Items]
Amortization expense related to intangible assets				$ 0.6
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Useful life		5 years
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	Sep. 30, 2016	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
2016	$ 184
2017	610
2018	409
2019	180
Total	$ 1,383	$ 1,934

RESTRUCTURING AND ASSET IMPAIRMENT CHARGES (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016
Restructuring Cost and Reserve [Line Items]
Employee severance and benefit arrangements	$ 1,308	$ 0
Asset impairments	1,409	0
Total restructuring and asset impairment charges	$ 2,717	$ 0
Restructuring Plan 2016
Restructuring Cost and Reserve [Line Items]
Asset impairments			$ 1,409
Total restructuring and asset impairment charges			2,717
Employee Severance \| Restructuring Plan 2016
Restructuring Cost and Reserve [Line Items]
Workforce reduction, percentage	11.00%
Asset impairments			0
Total restructuring and asset impairment charges			$ 1,308

RESTRUCTURING AND ASSET IMPAIRMENT CHARGES - Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016
Restructuring Reserve [Roll Forward]
Charges	$ 2,717	$ 0
Non-cash settlement	(1,409)	$ 0
Restructuring Plan 2016
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Beginning Balance			$ 0
Charges			2,717
Cash payments			(85)
Non-cash settlement			(1,409)
Restructuring Reserve, Ending Balance	1,223		1,223
Employee Severance \| Restructuring Plan 2016
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Beginning Balance			0
Charges			1,308
Cash payments			(85)
Non-cash settlement			0
Restructuring Reserve, Ending Balance	1,223		1,223
Asset Impairments \| Restructuring Plan 2016
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Beginning Balance			0
Charges			1,409
Cash payments			0
Non-cash settlement			(1,409)
Restructuring Reserve, Ending Balance	$ 0		$ 0

DEBT - Narrative (Details) - USD ($)	3 Months Ended
DEBT - Narrative (Details) - USD ($)	Sep. 30, 2016	Jul. 31, 2016	Dec. 31, 2015	Dec. 18, 2015
Short-term Debt [Line Items]
Outstanding borrowings	$ 12,450,000		$ 17,000,000
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
Amount of liquidity required for debt compliance	15,000,000.0
Amount of undrawn credit for debt compliance	5,000,000.0
Outstanding borrowings	12,500,000
Remaining borrowing capacity	$ 8,800,000
Weighted average interest rate	5.00%
Line of Credit \| Wells Fargo Bank \| Revolving credit facility \| Amendment To Revolver
Short-term Debt [Line Items]
Amount of liquidity required for debt compliance	$ 15,000,000.0
Amount of undrawn credit for debt compliance	$ 5,000,000.0	$ 12,500,000.0
Line of Credit \| Wells Fargo Bank \| Revolving credit facility \| LIBOR \| Minimum
Short-term Debt [Line Items]
Basis spread on variable rate	1.00%
Unused capacity, commitment fee percentage	0.25%
Line of Credit \| Wells Fargo Bank \| Revolving credit facility \| LIBOR \| Maximum
Short-term Debt [Line Items]
Basis spread on variable rate	3.75%
Unused capacity, commitment fee percentage	0.375%

DEBT - Term Loan (Details) - USD ($) $ in Thousands	1 Months Ended
DEBT - Term Loan (Details) - USD ($) $ in Thousands	Jul. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Line of Credit Facility [Line Items]
Long-term debt		$ 24,005	$ 0
Tennenbaum Capital Partners, LLC
Line of Credit Facility [Line Items]
Interest rate during period	10.25%
Commitment fee percentage	3.30%
Closing fee (as a percent)	10.00%
Tennenbaum Capital Partners, LLC \| Secured debt
Line of Credit Facility [Line Items]
Long-term debt	$ 25,000
LIBOR \| Tennenbaum Capital Partners, LLC
Line of Credit Facility [Line Items]
Interest rate during period	9.5625%
Reduction of interest rate during period (as a percent)	1.00%
Minimum \| Tennenbaum Capital Partners, LLC
Line of Credit Facility [Line Items]
Prepayment fee (as a percent)	1.00%
Maximum \| Tennenbaum Capital Partners, LLC
Line of Credit Facility [Line Items]
Prepayment fee (as a percent)	3.00%

DEBT - Long term debt (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Debt Disclosure [Abstract]
Term loan	$ 25,000	$ 0
Less unamortized discount and issuance costs	(995)	0
Carrying amount of debt	24,005	0
Less current portion	(1,197)	0
Long-term debt	$ 22,808	$ 0

DEBT - Maturities (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Debt Disclosure [Abstract]
2016	$ 0
2017	3,032
2018	7,824
2019	8,665
2020	5,479
Amount borrowed	$ 25,000	$ 0

COMMITMENTS AND CONTINGENCIES - (Details) $ in Millions	Sep. 30, 2016 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Cash on hand	$ 24.1

SALE OF COMMON STOCK (Details) - USD ($) $ / shares in Units, $ in Thousands			9 Months Ended
	Oct. 11, 2016	Sep. 28, 2016	Sep. 30, 2016	Sep. 30, 2015
Equity [Abstract]
Proceeds from public offering of common stock, net of underwriting fees		$ 14,000	$ 14,593	$ 0
Subsequent Event
Subsequent Event [Line Items]
Stock issued, value, stock options exercised, net	$ 2,200
Common Stock
Subsequent Event [Line Items]
Common stock issued during period		13,000,000
Shares issued, price per share (in USD per share)		$ 1.20
Common Stock \| Over-Allotment Option \| Subsequent Event
Subsequent Event [Line Items]
Common stock issued during period	1,950,000

STOCK-BASED COMPENSATION - Summary of Stock Option Activity (Details) shares in Thousands	9 Months Ended
	Sep. 30, 2016 $ / shares shares
Number of Shares Outstanding
Outstanding, beginning balance (in shares) \| shares	8,173
Granted (in shares) \| shares	2,367
Exercised (in shares) \| shares	(374)
Canceled (in shares) \| shares	(831)
Outstanding, ending balance (in shares) \| shares	9,335
Weighted- Average Exercise Price per Share
Outstanding, beginning balance (in usd per share) \| $ / shares	$ 5.36
Granted (in usd per share) \| $ / shares	2.15
Exercised (in usd per share) \| $ / shares	0.39
Canceled (in usd per share) \| $ / shares	7.01
Outstanding, ending balance (in usd per share) \| $ / shares	$ 4.60

STOCK-BASED COMPENSATION - Narrative (Details) $ in Millions	9 Months Ended
	Sep. 30, 2016 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of options exercised during period	$ 0.7
Intrinsic value of options outstanding	1.1
Total unrecognized compensation cost	$ 12.5
Weighted-average recognition period for unrecognized compensation cost	2 years 3 months 6 days
Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of stock vested during period	$ 0.8
Intrinsic value of restricted stock units outstanding	$ 0.9

STOCK-BASED COMPENSATION - Summary of Restricted Stock Unit Activity (Details) - Restricted stock units shares in Thousands	9 Months Ended
	Sep. 30, 2016 $ / shares shares
RSUs
Outstanding, beginning balance (in shares) \| shares	1,313
Granted (in shares) \| shares	54
Vested (in shares) \| shares	(432)
Canceled (in shares) \| shares	(206)
Outstanding, ending balance (in shares) \| shares	729
Weighted Average Fair Value per Share at Grant Date
Outstanding, beginning balance (in usd per share) \| $ / shares	$ 9.31
Granted (in usd per share) \| $ / shares	1.99
Vested (in usd per share) \| $ / shares	9.13
Canceled (in usd per share) \| $ / shares	7.41
Outstanding, ending balance (in usd per share) \| $ / shares	$ 9.41

STOCK-BASED COMPENSATION - Summary of the Components of Total Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Allocation of Stock-based Compensation Expense Included in the Consolidated Statement of Operations [Abstract]
Total stock-based compensation expense	$ 2,532	$ 3,283	$ 8,239	$ 9,579
Cost of revenues
Allocation of Stock-based Compensation Expense Included in the Consolidated Statement of Operations [Abstract]
Total stock-based compensation expense	295	331	907	913
Research and development
Allocation of Stock-based Compensation Expense Included in the Consolidated Statement of Operations [Abstract]
Total stock-based compensation expense	941	1,141	3,047	3,379
Sales and marketing
Allocation of Stock-based Compensation Expense Included in the Consolidated Statement of Operations [Abstract]
Total stock-based compensation expense	560	803	1,760	2,510
General and administrative
Allocation of Stock-based Compensation Expense Included in the Consolidated Statement of Operations [Abstract]
Total stock-based compensation expense	$ 736	$ 1,008	$ 2,525	$ 2,777

STOCK-BASED COMPENSATION - Summary of Stock-Based Compensation Associated with Each Type of Award (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 2,532	$ 3,283	$ 8,239	$ 9,579
Stock options and restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	1,983	2,753	6,703	8,153
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 549	$ 530	$ 1,536	$ 1,426

STOCK-BASED COMPENSATION - Summary of the Weighted-Average Grant Date Fair Value of Options Granted (Details) - Stock options - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
The fair value of each option granted during the periods
Weighted average grant date fair value (in usd per share)	$ 1.25	$ 3.01	$ 1.31	$ 5.40
Expected term (in years)	4 years 6 months	4 years 7 months 20 days	4 years 6 months	4 years 6 months
Expected volatility	84.70%	72.20%	79.80%	72.10%
Annual risk-free rate of return	1.10%	1.50%	1.10%	1.40%
Dividend yield	0.00%	0.00%	0.00%	0.00%

INCOME TAXES - Narrative (Details) $ in Millions	3 Months Ended
INCOME TAXES - Narrative (Details) $ in Millions	Jun. 30, 2016 USD ($)
Income Tax Disclosure [Abstract]
Deferred tax liabilities, undistributed foreign earnings	$ 0.1
Income (loss) from continuing operations before income taxes, foreign	$ 4.5

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		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Numerator:
Net income (loss)	$ (18,756)	$ 624	$ (54,274)	$ (6,299)
Denominator:
Shares used in per share calculation, basic	47,278	44,734	46,704	44,339
Effect of dilutive securities
Employee stock-based awards	0	3,261	0	0
Warrants	0	1	0	0
Weighted average common shares outstanding for diluted calculation	47,278	47,996	46,704	44,339
Net income (loss) per share, basic (in usd per share)	$ (0.40)	$ 0.01	$ (1.16)	$ (0.14)
Net income (loss) per share, diluted (in usd per share)	$ (0.40)	$ 0.01	$ (1.16)	$ (0.14)
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	10,268	6,340	10,023	10,380

NET INCOME (LOSS) PER SHARE - Schedule of Potentially Dilutive Securities Excluded from the Computation of Diluted Net Loss Per Share (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
The potential common shares outstanding that were excluded from the computation of diluted net loss per share attributable to common stockholders
Total (in shares)	10,268	6,340	10,023	10,380
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)	9,383	4,817	8,944	8,718
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)	840	1,523	994	1,551
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)	45	0	85	111