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Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2013	Feb. 28, 2014	Jun. 30, 2013
Document and Entity Information [Abstract]
Entity Registrant Name	Enphase Energy, Inc.
Entity Central Index Key	0001463101
Document Type	10-K
Document Period End Date	Dec. 31, 2013
Amendment Flag	false
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		42,236,859
Entity Well-Known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 113.1

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 38,190	$ 45,294
Accounts receivable, net of allowances of $2,000 and $1,177	32,084	27,743
Inventory	16,580	19,843
Prepaid expenses and other	3,655	2,118
Total current assets	90,509	94,998
Property and equipment, net	24,853	25,541
Other assets	1,307	1,752
Total assets	116,669	122,291
Current liabilities:
Accounts payable	7,363	11,272
Accrued liabilities	19,722	19,266
Deferred revenues	2,773	933
Current portion of term loans	3,507	2,384
Total current liabilities	33,365	33,855
Long-term liabilities:
Deferred revenues	11,284	7,537
Warranty obligations	25,490	15,260
Other liabilities	1,154	307
Term loans	5,170	8,677
Total long-term liabilities	43,098	31,781
Total liabilities	76,463	65,636
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; 42,123 and 40,856 shares issued and outstanding at December 31, 2013 and 2012, respectively	0	0
Additional paid-in capital	192,916	183,629
Accumulated deficit	(152,939)	(127,026)
Accumulated other comprehensive income	229	52
Total stockholders’ equity	40,206	56,655
Total liabilities and stockholders’ equity	$ 116,669	$ 122,291

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2013	Dec. 31, 2012
Allowances, accounts receivable	$ 2,000	$ 1,177
Preferred stock, par value (usd per share)	$ 0.00001	$ 0.00001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (usd per share)	$ 0.00001	$ 0.00001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	42,123,000	40,856,000
Common stock, shares outstanding	42,123,000	40,856,000

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net revenues	$ 232,846	$ 216,678	$ 149,523
Cost of revenues	165,430	161,390	120,454
Gross profit	67,416	55,288	29,069
Operating expenses:
Research and development	34,524	35,601	25,099
Sales and marketing	31,080	25,973	17,454
General and administrative	23,970	24,875	15,228
Total operating expenses	89,574	86,449	57,781
Loss from operations	(22,158)	(31,161)	(28,712)
Other income (expense), net:
Interest expense	(2,055)	(6,436)	(3,006)
Other income (expense)	(837)	30	(572)
Total other expense, net	(2,892)	(6,406)	(3,578)
Loss before income taxes	(25,050)	(37,567)	(32,290)
Provision for income taxes	(863)	(651)	0
Net loss attributable to common stockholders	$ (25,913)	$ (38,218)	$ (32,290)
Net loss per share attributable to common stockholders, basic and diluted (usd per share)	$ (0.62)	$ (1.24)	$ (25.73)
Shares used in computing net loss per share attributable to common stockholders, basic and diluted	41,647	30,740	1,255

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net loss attributable to common stockholders	$ (25,913)	$ (38,218)	$ (32,290)
Other comprehensive income (loss):
Foreign currency translation adjustments	177	(31)	83
Other comprehensive income (loss):	177	(31)	83
Comprehensive loss attributable to common stockholders	$ (25,736)	$ (38,249)	$ (32,207)

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Net Income
-URI http://asc.fasb.org/extlink&oid=6518256

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
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-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Reference 6: http://www.xbrl.org/2003/role/presentationRef
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-Topic 944
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.22)
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Other Comprehensive Income
-URI http://asc.fasb.org/extlink&oid=6519514

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e565-108580

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 19
-Article 5

Reference 10: http://www.xbrl.org/2003/role/presentationRef
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-Name Regulation S-X (SX)
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-Section 04
-Paragraph 20
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+ Details

Consolidated Statement of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Convertible Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income
BALANCE at Dec. 31, 2010	$ 38,481	$ 93,596	$ 0	$ 1,403	$ (56,518)	$ 0
BALANCE (in shares) at Dec. 31, 2010		22,221	843
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Private placement of common stock at $5.27 per share	1,858		$ 0	1,858
Private placement of common stock at $5.27 per share (in shares)			353
Exercise of stock options	$ 190		$ 0	190
Exercise of stock options (in shares)	502		502
Stock-based compensation	$ 2,120			2,120
Fair value of warrants and common stock issued in connection with convertible notes	2,312			2,312
Fair value of beneficial conversion feature upon issuance of convertible notes	1,165			1,165
Fair value of beneficial conversion feature from accrued paid-in-kind interest of convertible notes	55			55
Issuance of common stock upon exercise of warrants	0
Net loss	(32,290)				(32,290)
Foreign currency translation adjustment	83					83
BALANCE at Dec. 31, 2011	$ 13,974	$ 93,596	$ 0	9,103	(88,808)	83
BALANCE (in shares) at Dec. 31, 2011		22,221	1,698
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	59
Stock-based compensation	$ 4,766			4,766
Common stock issued upon initial public offering (“IPO”), net of offering costs	53,826		$ 0	53,826
Common stock issued upon initial public offering (“IPO”), net of offering costs (in shares)			10,315
Issuance of common stock under employee stock plans	255		$ 0	255
Issuance of common stock under employee stock plans (in shares)			138
Conversion of convertible preferred stock into common stock upon IPO	0	$ (93,596)	$ 0	93,596
Conversion of convertible preferred stock into common stock upon IPO (in shares)		(22,221)	25,171
Conversion of convertible notes and paid-in-kind interest into common stock upon IPO	21,204		$ 0	21,204
Conversion of convertible notes and paid-in-kind interest into common stock upon IPO (in shares)			3,534
Reclassification of preferred stock warrant liability to APIC upon IPO	879			879
Issuance of common stock upon exercise of warrants	21,204
Net loss	(38,218)				(38,218)
Foreign currency translation adjustment	(31)					(31)
BALANCE at Dec. 31, 2012	$ 56,655	$ 0	$ 0	183,629	(127,026)	52
BALANCE (in shares) at Dec. 31, 2012		0	40,856
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	822
Stock-based compensation	$ 6,849			6,849
Issuance of common stock under employee stock plans	2,438		$ 0	2,438
Issuance of common stock under employee stock plans (in shares)			1,255
Issuance of common stock upon exercise of warrants	0		$ 0	0
Issuance of common stock upon exercise of warrants (in shares)			12
Net loss	(25,913)				(25,913)
Foreign currency translation adjustment	177					177
BALANCE at Dec. 31, 2013	$ 40,206	$ 0	$ 0	$ 192,916	$ (152,939)	$ 229
BALANCE (in shares) at Dec. 31, 2013		0	42,123

Consolidated Statement of Stockholders' Equity (Parenthetical) - $ / shares	Apr. 04, 2012	Dec. 31, 2011
Common stock issued, price per share (usd per share)	$ 6.00	$ 5.27

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities:
Net loss	$ (25,913)	$ (38,218)	$ (32,290)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	6,981	5,568	3,032
Provision for doubtful accounts	678	1,068	127
Net loss on disposal of assets	82	120	0
Non-cash interest expense	429	4,777	1,835
Stock-based compensation	6,849	4,766	2,120
Change in fair value of convertible preferred stock warrants	0	(520)	321
Changes in operating assets and liabilities:
Accounts receivable	(5,019)	(11,040)	(9,874)
Inventory	3,263	(8,615)	(6,708)
Prepaid expenses and other assets	(1,450)	(711)	(1,648)
Accounts payable, accrued liabilities and warranty obligations	7,641	16,774	17,275
Deferred revenues	5,587	(18,614)	25,443
Net cash used in operating activities	(872)	(44,645)	(367)
Cash flows from investing activities:
Purchases of property and equipment	(6,257)	(12,990)	(14,662)
Net cash used in investing activities	(6,257)	(12,990)	(14,662)
Cash flows from financing activities:
Proceeds from issuance of convertible notes	0	0	20,000
Proceeds from private placement of common stock	0	0	1,858
Principal payments under capital leases	(40)	(96)	(169)
Proceeds from borrowings under term loans	0	10,000	9,898
Repayments of term loans	(2,447)	(14,103)	(1,863)
Proceeds from issuance of common stock under employee stock plans	2,429	255	190
Proceeds from issuance of common stock in IPO, net of underwriting discounts and commissions	0	58,609	0
Net cash (used in) provided by financing activities	(58)	51,436	26,482
Effect of exchange rate changes on cash	83	(31)	78
Net (decrease) increase in cash and cash equivalents	(7,104)	(6,230)	11,531
Cash and cash equivalents — Beginning of period	45,294	51,524	39,993
Cash and cash equivalents — End of period	38,190	45,294	51,524
Supplemental disclosures of cash flow information:
Cash paid for interest	1,391	1,681	1,235
Cash paid for income taxes	899	0	0
Non-cash financing and investing activities:
Assets acquired under capital lease	0	0	295
Purchases of property and equipment included in accounts payable	837	772	903
Offering costs not yet paid	0	0	371
Conversion of convertible notes into common stock upon IPO	0	21,204	0
Reclassification of convertible preferred stock warrant liability to additional paid-in capital upon IPO	0	879	0
Common Stock
Cash flows from financing activities:
Payment of offering costs	0	(2,198)	(2,585)
Convertible debt
Cash flows from financing activities:
Payments of costs related to issuance of convertible notes and financing costs	0	0	(274)
Debt, excluding convertible debt
Cash flows from financing activities:
Payments of costs related to issuance of convertible notes and financing costs	$ 0	$ (1,031)	$ (573)

Description of Business	12 Months Ended
Description of Business	Dec. 31, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
DESCRIPTION OF BUSINESS	DESCRIPTION OF BUSINESS Enphase Energy, Inc. and subsidiaries (the “Company”) designs, develops, and sells microinverter systems for the solar photovoltaic industry. The Company was incorporated in 2006 and began selling its products in 2008. The Company’s microinverter system consists of (i) an Enphase microinverter and related accessories that convert direct current (“DC”) power to grid-compliant alternating current (“AC”) power; (ii) an Envoy communications gateway device that collects and transmits performance information from each solar module to the Company’s hosted data center; and (iii) the Enlighten web-based software platform that collects and processes this information to enable customers to monitor and manage their solar power systems. The Company sells microinverter systems primarily to distributors who resell them to solar installers. The Company also sells directly to large installers as well as through original equipment manufacturers (“OEMs”) and strategic partners.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2013

Accounting Policies [Abstract]

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Principles of Consolidation

The accompanying consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.

Use of Estimates

The preparation of the Company’s consolidated financial statements in conformity with accounting principles generally accepted in the United States of America 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. 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.

Risks and Uncertainties

The Company is subject to risks inherent in a business with a limited operating history, including, but not limited to, new and rapidly evolving markets, advances and trends in the development of new technology and services, unfavorable economic and market conditions, competition from larger and more established companies, limited management resources and dependence on a limited number of contract manufacturers and suppliers. The inability to anticipate or to respond adequately to technological developments in the Company's industry, changes in customer or supplier requirements, or changes in regulatory requirements or industry standards could have a material adverse effect on the Company's business and operating results.

Revenue Recognition

The Company generates revenue from sales of its microinverter systems, which include microinverter units and related accessories, an Envoy communications gateway device, and an Enlighten web-based monitoring service, to distributors, large installers, OEMs and strategic partners. Enlighten service revenue represented less than 1% of the total revenues for all periods presented.

Revenues from sales of microinverters and related accessories, and communication gateways are recognized when: (i) persuasive evidence of an arrangement exists; (ii) delivery of the products has occurred in accordance with the terms of the sales agreement and title of and risk of loss have passed to the customer; (iii) the sale price is fixed or determinable; and (iv) collection is reasonably assured. Provisions for rebates, sales incentives, and discounts to customers are accounted for as reductions in revenue in the same period the related sales are recorded.

Sales of an Envoy communications gateway device include the Enlighten web-based monitoring service. The allocation of revenue between the two deliverables is based on the Company's best estimate of selling price determined by considering multiple factors including, internal costs, gross margin and historical pricing practices. After allocating the overall consideration from such sale to each deliverable using a best estimate of the selling price, (i) revenue from the sale of Envoy devices is recognized upon shipment, assuming all other revenue recognition criteria have been met and (ii) revenue from the web-based monitoring service is recognized ratably over the estimated economic life of the related Envoy devices of 10 years.

Deferred revenues consist of payments received from customers in advance of revenue recognition for the Company’s products and services described above. As of December 31, 2013 and 2012, deferred revenues consist entirely of service revenue.

Cost of Revenues

The Company includes the following in cost of revenues: product costs, warranty, manufacturing personnel and logistics costs, inventory write-downs, hosting services costs related to the Company’s Enlighten service offering, and depreciation and amortization of manufacturing test equipment.

Cash and Cash Equivalents

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

Fair Value of Financial Instruments

The carrying amounts of cash and cash equivalents, accounts receivable and accounts payable approximate fair value due to their relatively short-term nature. The carrying values of the Company's variable rate term loans approximate fair value.

Derivative Instruments

The Company operates and conducts business in foreign countries where its foreign entities use the local currency as their respective functional currency. As a result, the Company is exposed to movements in foreign currency exchange rates. The Company utilizes foreign currency forward contracts to reduce the impact of foreign currency fluctuations related to anticipated cash receipts from expected future revenues denominated in Euros and intercompany transaction gains or losses. The foreign currency forward contracts are accounted for as derivatives whereby the fair value of the contracts is reported as other current assets or current liabilities in the accompanying consolidated balance sheets, and gains and losses resulting from changes in the fair value are reported in other income (expense), net, in the accompanying consolidated statements of operations.

Allowances for Doubtful Accounts

The Company maintains allowances for doubtful accounts for uncollectible accounts receivable. Management estimates anticipated losses from doubtful accounts based on days past due, collection history and the financial health of customers. The allowance for doubtful accounts was $2.0 million and $1.2 million at December 31, 2013 and 2012, respectively. The following table sets forth activities in the allowance for doubtful accounts for the periods indicated:



	December 31,
	2013		2012			2011
Balance, at beginning of year	$	1,177	$	144		$	17
Charged to expenses	678		1,068			127
Charged to Other Accounts	145		(35		)	—
Balance, at end of year	$	2,000	$	1,177		$	144

Inventory

Inventory is valued at the lower of cost or market. The Company determines cost on a first-in first-out basis. Certain factors could affect the realizable value of its inventory, including customer demand and market conditions. Management assesses the valuation on a quarterly basis and writes down the value for any excess and obsolete inventory based upon expected demand, anticipated sales price, effect of new product introductions, product obsolescence, customer concentrations, product merchantability and other factors. Inventory write-downs are equal to the difference between the cost of inventories and their estimated net realizable market value.

Property and Equipment

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

Capitalized Software Costs

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

Long-Lived Assets

Management evaluates long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to future undiscounted net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets.

Warranty Obligations

Microinverters Sold Through December 31, 2013

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

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

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

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

If actual failure rates, claim rates, or replacement costs differ from the Company’s estimates in future periods, changes to these estimates would be required, resulting in increases or decreases in the Company’s warranty obligations. Such increases or decreases could be material.

Fair Value Option for Microinverters Sold Since January 1, 2014

The Company’s warranty obligations related to microinverters sold since January 1, 2014 provide the Company the right, but not the requirement, to assign its warranty obligations to a third-party. Pursuant to Accounting Standards Codification ("ASC") 820, Fair Value Measurement, such warranties are eligible to be accounted for at fair value. The Company expects to elect the fair value option to measure all eligible microinverter warranties for microinverters sold subsequent to January 1, 2014.

In addition to the key estimates of failure rates, claim rates and replacement costs described above, the fair value of warranty obligations will require the use of certain Level 3 inputs which are unobservable and significant to the overall fair value measurement. Such additional assumptions will include a discount rate based upon the Company's credit-adjusted risk-free rate and a hypothetical profit margin and risk premium required of a hypothetical market participant to assume the obligation. Warranty obligations initially recorded at fair value (computed using an expected present value technique) at the time of sale will be subsequently re-measured to fair value at each reporting date. In addition, the fair value of the liability will be accreted over the corresponding term of the warranty of up to 25 years using the effective interest method. Any changes in fair value of the liability from period-to-period, including accretion expense, will be recognized in cost of revenues.

If actual failure rates, claim rates, replacement costs, discount rate or the other additional assumptions differ from the Company’s estimates in future periods, changes to these estimates would be required, resulting in increases or decreases in the Company’s warranty obligations. Such increases or decreases could be material.

As of December 31, 2013, warranty obligations were $30.4 million. Periodic adjustments necessitated by actual experience of claims and any future changes in estimates to this liability associated with sales prior to December 31, 2013 will continue to be accounted for on an undiscounted basis.

Research and Development Costs

The Company expenses research and development costs as incurred. Research and development costs totaled $34.5 million, $35.6 million and $25.1 million in 2013, 2012 and 2011, respectively.

Stock-Based Compensation

Share-based payments are required to be recognized in the Company’s consolidated statements of operations based on their fair values and the estimated number of shares expected to vest. The Company measures stock-based compensation expense for all share-based payment awards, including stock options made to employees and directors, based on the estimated fair values on the date of the grant. The fair value of stock options granted is estimated using the Black-Scholes option valuation model. The fair value of restricted stock units granted is determined based on the price of the Company's common stock on the date of grant. Stock-based compensation, net of estimated forfeitures, is recognized on a straight-line basis over the requisite service period, which is typically four years.

Comprehensive Loss

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

Income Taxes

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

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

Inventory

12 Months Ended

Dec. 31, 2013

Inventory Disclosure [Abstract]

INVENTORY

Inventory as of December 31, 2013 and 2012, consists of the following (in thousands):



	December 31,
	2013		2012
Raw materials	$	1,428	$	2,223
Finished goods	15,152		17,620
Total inventory	$	16,580	$	19,843

In 2013, no significant write-downs of inventories were made. In 2012 and 2011, the Company recorded write-downs of inventories of $0.8 million and $2.7 million, respectively.

Property and Equipment, Net

12 Months Ended

Dec. 31, 2013

Property, Plant and Equipment [Abstract]

PROPERTY AND EQUIPMENT, NET

As of December 31, 2013 and 2012, property and equipment, net consists of the following (in thousands):



	Estimated Useful Life (Years)	December 31,
	Estimated Useful Life (Years)	2013			2012
Equipment and machinery	5	$	21,853		$	18,723
Furniture and fixtures	5–7	2,837			2,788
Computer equipment	3	1,842			1,688
Capitalized software	3–5	7,343			5,760
Leasehold improvements	3–10	5,881			5,642
Construction in progress		1,703			1,419
Total		41,459			36,020
Less accumulated depreciation and amortization		(16,606		)	(10,479		)
Property and equipment, net		$	24,853		$	25,541

Depreciation expense was $5.5 million, $4.4 million and $2.3 million for 2013, 2012 and 2011, respectively.

Capitalized Developed or Purchased Internal-Use Software—Capitalized software costs are being amortized ratably over the estimated useful lives and are included within amortization expense in the amount of $1.5 million, $1.2 million and $0.7 million for 2013, 2012 and 2011, respectively.

The following table summarizes capitalized internal-use software costs (in thousands):



	December 31, 2013				December 31, 2012
	Gross Cost		Net of Accumulated Amortization		Gross Cost		Net of Accumulated Amortization
Developed internal-use software	$	3,322	$	1,333	$	2,570	$	1,053
Purchased software for internal use	4,021		2,311		3,190		2,227
Total software	$	7,343	$	3,644	$	5,760	$	3,280

The estimated future aggregate amortization expense for existing internal-use software as of December 31, 2013 is expected to be $1.7 million in 2014, $1.2 million in 2015 and $0.7 million in 2016.

Warranty Obligations

12 Months Ended

Dec. 31, 2013

Product Warranties Disclosures [Abstract]

WARRANTY OBLIGATIONS

The Company’s warranty activities during 2013, 2012 and 2011 were as follows (in thousands):



	December 31,
	2013			2012			2011
Balance, at beginning of year	$	21,338		8,738			$	2,668
Accruals for warranties issued during the year	6,303			8,218			5,279
Changes in estimates	10,303			7,607			1,751
Settlements	(7,512		)	(3,225		)	(960		)
Balance, at end of year	30,432			21,338			8,738
Less current portion included in accrued liabilities	(4,942		)	(6,078		)	(2,005		)
Long-term portion	$	25,490		$	15,260		$	6,733

The Company sold approximately 1.0 million second generation microinverters from 2009 through mid-2012. The Company has sold approximately 3.5 million third generation microinverters since mid-2012 and continues to sell such third generation microinverters. The Company has sold 150,000 fourth generation microinverters since mid-2013.

Changes in Estimates

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

2013

In 2013, primarily in the second, third and fourth quarters, the Company experienced actual failures of its second generation microinverters that exceeded its then current failure rate estimate. Based on continuing analysis of field performance data and diagnostic root-cause failure analysis performed on returned units, the Company concluded that it was necessary to increase the estimated failure rates for its second generation product and recorded additional warranty expense of $19.5 million in 2013 (including $3.5 million in the three months ended December 31, 2013). During the third quarter of 2013, the Company recorded a reduction to warranty expense of $3.1 million related to a decrease in the expected failure rate of the Company's third generation product. The Company concluded that there was sufficient historical data of actual field performance of previously sold third generation products to support a lower estimated failure rate.

In addition, the Company updated its estimated claim rates for its second and third generation products resulting in a decrease to warranty expense of $4.2 million. The revision to estimated claim rates was based on the Company’s observed historical end user behavior and assumptions with respect to expected customer behavior over the 15 or 25 year warranty term.

Also, the Company decreased warranty expense by $1.9 million (including $1.7 million in the three months ended December 31, 2013), primarily to reflect estimated lower costs to produce fourth generation microinverters to fulfill warranty obligations for second and third generation microinverters.

2012

In 2012, primarily in the third and fourth quarters, the Company experienced actual failures of its second generation microinverters that exceeded its then current failure rate estimate. Based on continuing analysis of field performance data and diagnostic root-cause failure analysis performed on returned units, the Company concluded that it was necessary to increase the estimated failure rates for its second generation product and recorded additional warranty expense of $10.2 million in 2012 (including $2.4 million in the three months ended December 31, 2012).

In the fourth quarter of 2012, the Company revised its claim rate estimate to reflect a decrease in the percentage of end users who are able to access their system’s performance data using the Enlighten monitoring service. Approximately 80 to 90 percent of end users have purchased systems that include Enlighten. End users who have not purchased Enlighten do not have access to the same inverter-level performance data as end users using Enlighten and, consequently are less likely to make warranty claims. In 2012, based on observation of historical results, the Company confirmed that non-Enlighten end users had a lower claim rate than originally estimated. As a result, warranty expense decreased by $0.5 million to reflect this information.

In addition, the Company recorded a reduction to warranty expense of $2.1 million related to replacement costs, primarily comprised of a $1.9 million reduction in shipping costs. Beginning in the third quarter of 2012, the Company revised its business practice to utilize non-expedited shipping terms for future replacement units, resulting in the reduction in estimated future replacement costs.

2011

In 2011, warranty expense included $1.8 million resulting from changes in estimates to reflect increased estimated replacement costs for second generation products.

Fair Value Measurements

12 Months Ended

Dec. 31, 2013

Fair Value Disclosures [Abstract]

FAIR VALUE OF FINANCIAL INSTRUMENTS

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 required to be 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.

Derivative Instruments—The Company utilizes foreign currency forward contracts to reduce the impact of foreign currency fluctuations arising from both sales and purchases denominated in Euros and the British Pound Sterling. As of December 31, 2013 and 2012, the aggregate gross notional amounts of outstanding foreign currency forward contracts were $12.5 million and $6.1 million, respectively. All outstanding open forward contracts at December 31, 2013 matured in January 2014.

The following table presents the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy at December 31, 2013 and 2012 (in thousands):



	Asset Derivatives				Liability Derivatives
	December 31, 2013		December 31, 2012		December 31, 2013		December 31, 2012
Foreign currency forward contracts (Level 2)	$	325	$	—	$	605	$	268

In 2013 and 2012, the Company recognized net losses of $0.4 million and $0.5 million related to foreign currency forward contracts, respectively.

Long-Term Debt

12 Months Ended

Dec. 31, 2013

Debt Disclosure [Abstract]

LONG-TERM DEBT

The Company’s long-term debt was comprised of the following at December 31, 2013 and 2012 (in thousands):



	December 31,
	2013			2012
Term loans	$	7,400		$	7,400
Equipment financing facility, net of unamortized discount of $31 and $94, respectively	1,277			3,661
Total debt	8,677			11,061
Less current portion	(3,507		)	(2,384		)
Long-term portion	$	5,170		$	8,677

As of December 31, 2013, the amount of future principal repayments due on the total debt is as follows (in thousands):



2014	$	3,538
2015	2,973
2016	2,197
Total	$	8,708

Revolving Credit Facility—The Company has a $50.0 million revolving credit facility (the “Revolver”) with Wells Fargo Bank, N.A. (“Wells Fargo”), which had a maturity date of November 7, 2015. On February 14, 2014, the Company entered into an amendment which granted an automatic extension of the maturity date from November 7, 2015 to November 7, 2016, provided the Company has not borrowed any amounts under the Additional Term Loans made available by Hercules Technology Growth Capital, Inc. ("Hercules") as described below, or otherwise restructure the Additional Term Loans to the satisfaction of Wells Fargo. The amount of loans available to be drawn 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. Wells Fargo and Hercules are parties to an intercreditor agreement, pursuant to which Hercules has a first lien on certain of the Company's assets and a second priority on its other assets. Subject to the intercreditor agreement, loans under the Revolver are secured by a pledge of substantially all of the Company's assets other than intellectual property. Loans 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 1.5% and 4.25% depending on the currency borrowed and the specific term of repayment. The Revolver contains customary affirmative and negative covenants and events of default, and requires the Company to maintain at least $15.0 million of liquidity at all times, of which at least $8.0 million ($5.0 million in the case the maturity date is November 7, 2016) must be undrawn availability. To date, the Company has not drawn on the Revolver and approximately $22.4 million was available for borrowing as of December 31, 2013 based on eligible accounts receivable and inventory balances pursuant to the agreement.

Term Loans—The Company has a loan and security agreement with Hercules, pursuant to which it borrowed $7.4 million (the "Initial Term Loan"). In addition, the Company may borrow an additional $15.6 million in term loans (the "Additional Term Loans"), which must be drawn, if at all, not later than March 31, 2014. To date, the Company has not, and does not intend to borrow any Additional Term Loans prior to its impending expiration on March 31, 2014. The Company used the proceeds of the Initial Term Loan to replenish cash on hand, which had previously been used to repay the approximately $7.5 million in other outstanding term loans. Loans under the Hercules facility bear interest at an annual rate equal to the higher of (i) the prime rate plus 8.25% or (b) 11.5%. All loans under the Hercules facility will mature on August 1, 2016. Interest is payable in cash on a monthly basis, and the loans will amortize in equal monthly installments commencing on March 1, 2014 for the Initial Term Loan. In addition, the facility includes a $0.6 million end of term charge due on August 1, 2016. Prepayments of loans under the facility are subject to early payment penalties. Loans under the Hercules facility are secured by a pledge of substantially all of the Company's assets other than intellectual property. The Hercules facility does not include any financial covenants. As of December 31, 2013, the outstanding principal balance under the Term Loans was $7.4 million, which solely relates to borrowings under the Initial Term Loan.

Equipment Financing Facility—The Company has an equipment financing facility with Hercules. The equipment financing facility has a variable interest rate set at the higher of 5.75% above the prime lending rate and 9.0% annually and expires July 1, 2014. This facility is secured by the financed equipment and restricts the Company’s ability to pay dividends and take on certain types of additional liens. As of December 31, 2013, the outstanding principal balance under the equipment financing facility was $1.3 million.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2013

Commitments and Contingencies Disclosure [Abstract]

COMMITMENTS AND CONTINGENCIES

Operating Leases—The Company leases office facilities under noncancelable operating leases that expire on various dates through 2022. The terms of the lease agreements generally provide for rental payments on a graduated basis, and certain leases require the Company to pay its portion of executory costs such as taxes, insurance, and operating expenses. The Company recognizes rent expense on a straight-line basis over the lease term.

Rent expense for 2013, 2012 and 2011 was $2.6 million, $2.4 million and $1.2 million, respectively.

The Company’s minimum lease payments under noncancelable operating leases, exclusive of executory costs, as of December 31, 2013 are as follows (in thousands):



2014	$	1,672
2015	1,749
2016	1,766
2017	1,555
2018	1,599
Thereafter	5,756
Total minimum lease payments	$	14,097

Purchase Obligations—The Company has contractual obligations to purchase goods and services, which specify fixed or minimum quantities to be purchased; fixed, minimum, or variable price provisions; and the approximate timing of the transaction. Purchase obligations do not include contracts that may be canceled without penalty.

The Company utilizes third parties to manufacture its products. As of December 31, 2013, the Company had purchase obligations with third party manufacturers and suppliers totaling approximately $87.6 million. Certain agreements specify future quantities and pricing of products to be supplied by the Company's contract manufacturers for periods up to seven years. Of the $87.6 million included in purchase obligations, $72.5 million are cancelable; however if canceled, the agreement requires the Company to pay cancellation penalties of up to $5.6 million.

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

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Dec. 31, 2013
Equity [Abstract]
STOCKHOLDERS' EQUITY	STOCKHOLDERS' EQUITY Initial Public Offering On April 4, 2012, the Company completed its initial public offering ("IPO"), issuing 10,315,151 shares of common stock at an offering price of $6.00 per share. The net proceeds from the sale of the shares were $53.8 million, after deducting the underwriters’ discounts and commissions of $3.3 million and other offering costs of $4.8 million. Upon consummation of the IPO, the Company’s 22,220,856 outstanding shares of convertible preferred stock ($93.6 million carrying value) were automatically converted into 25,171,017 shares of common stock, and the $21.2 million outstanding balance of principal and accrued paid-in-kind interest in convertible notes were automatically converted into 3,533,988 shares of common stock at a conversion price equal to the IPO price of $6.00 per share. As a result, the Company recorded a charge of $2.8 million to interest expense in 2012 for the extinguishment of debt related to the unamortized debt issuance costs and debt discounts. Common Stock Warrants Prior to its IPO, the Company issued convertible preferred stock warrants in connection with several financing transactions. These warrants automatically converted into warrants to purchase common stock upon the consummation of the IPO. As of December 31, 2013, warrants to purchase 293,474 shares of the Company's common stock remained outstanding with exercise prices ranging from $5.27 to $6.17. Such warrants are exercisable and will expire on various dates from 2016 through 2021.

- 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 235
-SubTopic 10
-Section S99
-Paragraph 1
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
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-Topic 210
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-Paragraph 1
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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
-Publisher FASB
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Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (SX 210.3-04)
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
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-URI http://asc.fasb.org/extlink&oid=6405834&loc=d3e23285-112656

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Preferred Stock
-URI http://asc.fasb.org/extlink&oid=6521494

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21564-112644

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Paragraph d
-Article 4

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 29, 30, 31
-Article 5

Reference 16: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section E

Reference 17: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
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Reference 18: http://www.xbrl.org/2003/role/presentationRef
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Reference 19: http://www.xbrl.org/2003/role/presentationRef
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-Number 210
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+ Details

Stock-Based Compensation

12 Months Ended

Dec. 31, 2013

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

STOCK-BASED COMPENSATION

Description of Equity Incentive Plans

2006 Plan—Under the Company's 2006 Equity Incentive Plan (the “2006 Plan”), equity awards granted generally vest over a four-year period from the date of grant with a contractual term of up to 10 years. As of December 31, 2013, there were 5.2 million shares of common stock outstanding under the 2006 Plan. No further stock options or other stock awards may be granted under the 2006 Plan.

2011 Plan—Under the 2011 Equity Incentive Plan (the “2011 Plan”), the Company may, initially, issue up to 2,643,171 shares of its common stock pursuant to stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, performance-based stock awards, and other forms of equity compensation, or collectively, stock awards, all of which may be granted to employees, including officers, and to non-employee directors and consultants. Options granted under the 2011 Plan before August 1, 2012 generally expire 10 years after the grant date and options granted thereafter generally expire 7 years after the grant date. Equity awards granted under the 2011 Plan generally vest over a four-year period from the date of grant based on continued employment. The number of shares of the Company's common stock authorized for issuance under the 2011 Plan will automatically increase, on each January 1, by 4.5% of the total number of shares of the Company's common stock outstanding on December 31 of the preceding calendar year, or such lesser number of shares of common stock as determined by the board of directors. As of December 31, 2013, 586,524 shares of common stock remained available for issuance pursuant to future grants under the 2011 Plan. On January 1, 2014, the shares authorized for issuance under the 2011 Plan automatically increased by 1,895,541 shares.

2011 Employee Stock Purchase Plan—The 2011 Employee Stock Purchase Plan (“ESPP”) became effective immediately upon the execution and delivery of the underwriting agreement for the Company’s IPO on March 29, 2012. The ESPP initially authorizes the issuance of 669,603 shares of the Company's common stock pursuant to purchase rights granted to employees. The number of shares of common stock reserved for issuance will automatically increase, on each January 1, by 330,396 shares of the Company's common stock or a lesser number of shares of common stock as determined by the Company's board of directors.

The ESPP is implemented by concurrent offering periods and each offering period may contain up to four interim purchase periods. In general, offering periods consists of the 24 months periods commencing on each May 1 and November 1 of a calendar year.

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

As of December 31, 2013, there were 613,984 shares of the Company's common stock available for issuance under the ESPP. On January 1, 2014, the shares authorized for issuance under the ESPP automatically increased by 330,396 shares.

Valuation of Equity Awards

Stock Options

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


•	Expected term—The expected term of the option awards represents the period of time between the grant date of the option awards and the date the option awards are either exercised, converted or canceled, including an estimate for those option awards still outstanding.

•

Expected volatility—The Company uses the simplified method, as permitted by the SEC for companies with a limited history of stock option exercise activity, to determine the expected term for its option grants. Expected stock price volatility is determined based on an average of the historical volatilities of the common stock of several companies with characteristics similar to those of the Company.


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


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

The assumptions used in calculating fair values for stock options granted under the Plan and the resultant weighted-average estimated fair values for the periods presented are as follows:



	Year Ended December 31,
	2013			2012			2011
Expected term (in years)	4.4			5.7			6.0
Expected volatility	68.4		%	74.5		%	72.0		%
Annual risk-free rate of return	1.0		%	0.9		%	1.8		%
Dividend yield	—		%	—		%	—		%
Weighted-average fair value on grant date	$	3.84		$	4.69		$	5.08

Restricted Stock Units

The fair value of restricted stock units granted is determined based on the price of the Company's common stock on the date of grant.

Stock-Based Compensation Expense

The following table summarizes the components of total stock-based compensation expense included in the consolidated statement of operations for the periods presented (in thousands):



	Year Ended December 31,
	2013		2012		2011
Cost of revenues	$	438	$	196	$	39
Research and development	2,110		1,728		795
Sales and marketing	1,812		1,254		671
General and administrative	2,489		1,588		615
Total stock-based compensation expense	$	6,849	$	4,766	$	2,120

The following table summarizes stock-based compensation associated with each type of award:



	Year Ended December 31,
	2013		2012		2011
Stock options and restricted stock units	$	6,314	$	4,519	$	2,120
ESPP	535		247		—
Total stock-based compensation expense	$	6,849	4,766		$	2,120

As of December 31, 2013, there was approximately $13.2 million of total unrecognized compensation cost related to unvested equity awards, net of expected forfeitures, which is expected to be recognized over a weighted-average period of 2.6 years.

No income tax benefit has been recognized relating to stock-based compensation expense and no tax benefits have been realized from exercised stock options.

Equity Awards Activity

Stock Options

A summary of the Company’s stock option activity for 2013, 2012 and 2011 is as follows (in thousands, except per share data):



	Shares		Weighted- Average Exercise Price per Share
Options outstanding — December 31, 2010	5,802		$	0.90
Granted	1,110		6.16
Exercised	(502	)	0.38
Canceled	(154	)	2.82
Options outstanding — December 31, 2011	6,256		1.83
Granted	2,478		7.35
Exercised	(59	)	1.26
Canceled	(506	)	5.55
Options outstanding — December 31, 2012	8,169		3.28
Granted	1,506		7.17
Exercised	(822	)	1.69
Canceled	(344	)	7.74
Options outstanding — December 31, 2013	8,509		3.94

The following table summarizes information about stock options outstanding at December 31, 2013:



	Options Outstanding				Options Exercisable
Range of Exercise Prices	Number of Shares (in thousands)	Weighted- Average Remaining Life (in years)	Weighted- Average Exercise Price		Number of Shares (in thousands)	Weighted- Average Exercise Price
$0.27 —– $0.91	2,424	5.5	$	0.29	2,424	$	0.29
$1.63 —– $1.63	1,663	6.5	1.63		1,486	1.63
$2.00 —– $5.78	1,209	6.3	3.87		617	3.32
$5.87 —– $7.50	1,379	7.4	6.91		428	7.00
$7.68 —– $8.82	1,280	7.3	8.09		309	8.26
$9.40 —– $11.00	554	7.7	10.04		287	9.98
Total	8,509	6.6	3.94		5,551	2.45

The intrinsic value of options exercised during 2013 and 2012 was $3.2 million and $0.3 million, respectively. As of December 31, 2013, there were 8.3 million options outstanding that were vested and expected to vest. Such options have a weighted-average exercise price of $3.87 and a weighted-average remaining contractual term of6.5 years. As of December 31, 2013, the aggregate intrinsic value was $23.5 million for the 5.6 million exercisable shares. The intrinsic value is based on the Company’s common stock fair value of $6.34 per share as of December 31, 2013.

Restricted Stock Units

The following is a summary of restricted stock unit activity for 2013 and 2012 (in thousands, except per share data):



	Restricted Stock Units		Weighted Average Fair Value per Share at Grant Date
Outstanding at December 31, 2011	—		$	—
Granted	282		5.69
Vested	(20	)	2.00
Canceled	(14	)	6.90
Outstanding at December 31, 2012	248		5.53
Granted	285		6.92
Vested	(107	)	6.08
Canceled	(8	)	7.07
Outstanding at December 31, 2013	418		6.31

The intrinsic value of restricted stock units vested during 2013 and 2012 was $0.8 million and $39,000, respectively. As of December 31, 2013, the restricted stock units outstanding had a weighted average remaining contractual term of 1.6 years with an intrinsic value of $2.6 million.

ESPP

The following is a summary of ESPP activity for 2013 and 2012 and (in thousands, except per share data):



	Year Ended December 31,
	2013		2012
Proceeds from common stock issued under ESPP	$	1,047	$	185
Shares of common stock issued	327		59
Weighted-average price per share	$	3.20	$	3.14

Income Taxes

12 Months Ended

Dec. 31, 2013

Income Tax Disclosure [Abstract]

INCOME TAXES

No provision for U.S. federal or state income taxes has been made due to cumulative losses since the commencement of operations.

A provision for income taxes of $0.9 million and $0.7 million has been recognized for 2013 and 2012, respectively, related to the Company's foreign operations.

A reconciliation of total income tax expense and the amount computed by applying the federal statutory income tax rate of 34% to loss before income taxes for 2013, 2012 and 2011 is as follows (in thousands):



	Year Ended December 31,
	2013			2012			2011
Income tax benefit at statutory rate	$	(8,517	)	$	(12,773	)	$	(10,883	)
State taxes, net of federal benefit	(883		)	(1,478		)	(1,956		)
Change in valuation allowance	8,353			12,574			12,451
Stock-based compensation	1,191			1,128			479
Other	455			1,027			(91		)
Uncertain tax positions	264			173			—
Provision for income taxes	$	863		$	651		$	—

A summary of significant components of the Company’s deferred tax assets and liabilities as of December 31, 2013 and 2012 is as follows (in thousands):



	December 31,
	2013			2012
Current:
Reserves and allowances	$	14,521		$	11,523
Valuation allowance	(14,521		)	(11,523		)
Total current	—			—
Non-current:
Net operating losses	16,840			14,364
Stock-based compensation	1,531			919
Deferred revenue	2,730			1,425
Fixed assets and intangibles	11,670			10,301
Other	476			880
Valuation allowance	(33,245		)	(27,889		)
Total non-current	2			—
Deferred tax liability	—			—
Net deferred tax assets	$	2		$	—

Due to the history of losses the Company has generated since inception, the Company believes that it is more-likely-than-not that all of the deferred tax assets will not be realized as of December 31, 2013. Therefore, the Company has recorded a full valuation allowance on its deferred tax assets.

The Company has net operating loss carryforwards for federal and California income tax purposes of approximately $61.3 million and $53.0 million, respectively, as of December 31, 2013. The federal and state net operating loss carryforwards, if not utilized, will expire beginning in 2026 and 2016, respectively. Utilization of the net operating loss carryforwards may be subject to a substantial annual limitation due to the ownership change limitations provided by the Internal Revenue Code of 1986, as amended (the "Code"), and similar state provisions. The annual limitation may result in the expiration of net operating losses before utilization. The Company has not completed a study to assess whether an ownership change has occurred or whether there have been multiple ownership changes since the Company became a “loss corporation” under the Code. Due to the existence of the valuation allowance, it is not expected that any possible limitation will have an impact on the results of operations or financial position of the Company.

A share option exercise may result in a tax deduction prior to the actual recognition of the related excess tax benefit because the Company has a net operating loss carryforward. The Company's net operating losses include $201,000 of excess stock option benefits that will be reflected as a credit to additional paid-in capital when utilized.

The accounting for uncertain tax positions prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. The Company is required to recognize in the financial statements the impact of a tax position, if that position is more-likely-than-not of being sustained on audit, based on the technical merits of the position. The gross unrecognized tax benefits have increased from $160,000 at December 31, 2012 to $376,000 at December 31, 2013, due to increases in tax positions for the current year of $137,000 and increases in tax positions for prior year of $79,000. The unrecognized tax benefits of $376,000 at December 31, 2013, if recognized, would reduce the Company's annual effective tax rate. The Company also accrued interest and penalties of $47,000 related to unrecognized tax benefits during 2013.

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

The Company’s tax returns continue to remain subject to examination by U.S. federal authorities for the years 2010 through 2013 and by California state authorities for the years 2009 through 2013.

Concentration of Credit Risk and Major Customers	12 Months Ended
Concentration of Credit Risk and Major Customers	Dec. 31, 2013
Segment Reporting [Abstract]
CONCENTRATION OF CREDIT RISK AND MAJOR CUSTOMERS	CONCENTRATION OF CREDIT RISK AND MAJOR CUSTOMERS The Company is potentially subject to financial instrument concentration of credit risk through its cash and cash equivalents and accounts receivable. The Company places its cash and cash equivalents with high quality institutions and performs periodic evaluations of their relative credit standing. Accounts receivable can be potentially exposed to a concentration of credit risk with its major customers. As of December 31, 2013, the Company had amounts due from two customers that represented 16% and 10% of the total accounts receivable balance. As of December 31, 2012, its two largest accounts receivable balances represented 21% and 16% of the total accounts receivable balance. In 2013, three customers accounted for 15%, 14% and 11% of total net revenues. In 2012, two customers accounted for 16% and 11% of total net revenues. In 2011, three customers accounted for 17%, 11% and 10% of total net revenues.

Net Loss Per Share Attributable to Common Stockholders

12 Months Ended

Dec. 31, 2013

Earnings Per Share [Abstract]

NET LOSS PER SHARE ATTRIBUTABLE TO COMMON STOCKHOLDERS

In April 2012, all of the Company’s then outstanding convertible preferred stock automatically converted into common stock in connection with its IPO. For periods that ended prior to the conversion, basic and diluted net income per common share were presented in conformity with the two-class method required for participating securities.

Under the two-class method, net loss is allocated between common shares and other participating securities to the extent that the securities are required to share in the losses. The Company’s convertible preferred stock did not meet the definition of a participating security in periods of net losses as the convertible preferred stockholders did not have a contractual obligation to share in the Company’s losses. Accordingly, net losses were attributable to common stockholders. Subsequent to the Company’s IPO and the automatic conversion of the outstanding convertible preferred stock, the Company had no other participating securities and the two-class method is no longer applicable.

Basic net loss per share attributable to common stockholders is calculated by dividing net loss attributable to common stockholders by the weighted average number of shares outstanding for the period. Diluted net loss per share attributable to common stockholders is calculated by dividing net loss attributable to common stockholders by the weighted average number of common shares and potential dilutive common share equivalents outstanding during the period if the effect is dilutive. The Company’s potentially dilutive common shares include convertible notes and convertible preferred stock prior to their conversion, outstanding stock options and warrants and non-vested restricted stock units.

The following table presents the potential common shares outstanding that were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been anti-dilutive (in thousands):



	Year Ended December 31,
	2013	2012	2011
Convertible preferred stock	—	—	25,171
Stock options to purchase common stock	8,196	8,174	6,256
Convertible notes	—	—	2,328
Unvested restricted stock units	381	248	—
Warrants to purchase common stock	308	331	143
Convertible preferred stock warrants	—	—	215
Total	8,885	8,753	34,113

Segment and Geographic Information

12 Months Ended

Dec. 31, 2013

Segment Reporting [Abstract]

SEGMENT AND GEOGRAPHIC INFORMATION

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

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

Net Revenues



	Year Ended December 31,
	2013		2012		2011
United States	$	192,881	$	189,711	$	128,692
International	39,965		26,967		20,831
Total	$	232,846	$	216,678	$	149,523

Long-Lived Assets



	As of December 31,
	2013		2012		2011
United States	$	16,262	$	17,136	$	11,199
China	7,130		6,642		5,974
Other	1,461		1,763		1,238
Total	$	24,853	$	25,541	$	18,411

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8981-108599

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
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-Topic 280
-SubTopic 10
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Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e9031-108599

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 12: http://www.xbrl.org/2003/role/presentationRef
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Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8924-108599

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8906-108599

+ Details

Related Party Transactions	12 Months Ended
Related Party Transactions	Dec. 31, 2013
Related Party Transactions [Abstract]
RELATED PARTY TRANSACTIONS	RELATED PARTY TRANSACTIONS KPCB Holdings, Inc. ("KPCB"), as nominee for certain funds of Kleiner Perkins Caufield & Byers, owned approximately 11 percent of the Company's outstanding stock as of December 31, 2013. Revenues recognized from sales of microinverters to entities that are majority-owned by KPCB entities in 2013, 2012 and 2011 were $2.7 million, $16.8 million and $6.4 million, respectively.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References + Details

Quarterly Financial Information

12 Months Ended

Dec. 31, 2013

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Information

(Unaudited)

(In thousands, except per share data)



	Quarters Ended for Fiscal 2013
	March 31			June 30			September 30			December 31

Net revenues	$	45,577		$	58,167		$	62,046		$	67,056
Cost of revenues⁽¹⁾	33,376			41,883			44,611			45,560
Gross profit	12,201			16,284			17,435			21,496
Operating expenses:
Research and development	9,026			8,484			8,293			8,721
Sales and marketing	6,850			7,365			8,550			8,315
General and administrative	6,036			5,926			5,937			6,071
Total operating expenses	21,912			21,775			22,780			23,107
Loss from operations	(9,711		)	(5,491		)	(5,345		)	(1,611		)
Other expense, net	(513		)	(781		)	(815		)	(783		)
Loss before income taxes	(10,224		)	(6,272		)	(6,160		)	(2,394		)
Provision for income taxes	(182		)	(124		)	(141		)	(416		)
Net loss	$	(10,406	)	$	(6,396	)	$	(6,301	)	$	(2,810	)
Net loss per share, basic and diluted	$	(0.25	)	$	(0.15	)	$	(0.15	)	$	(0.07	)

	Quarters Ended for Fiscal 2012
	March 31			June 30			September 30			December 31
Net revenues	$	42,600		$	55,697		$	60,813		$	57,568
Cost of revenues⁽¹⁾	33,293			42,096			44,489			41,512
Gross profit	9,307			13,601			16,324			16,056
Operating expenses:
Research and development	7,842			8,655			10,571			8,533
Sales and marketing	5,049			6,360			7,039			7,525
General and administrative	5,696			6,091			6,911			6,177
Total operating expenses	18,587			21,106			24,521			22,235
Loss from operations	(9,280		)	(7,505		)	(8,197		)	(6,179		)
Other expense, net	(839		)	(3,729		)	(580		)	(1,258		)
Loss before income taxes	(10,119		)	(11,234		)	(8,777		)	(7,437		)
Provision for income taxes	(65		)	(151		)	(130		)	(305		)
Net loss	$	(10,184	)	$	(11,385	)	$	(8,907	)	$	(7,742	)
Net loss per share, basic and diluted	$	(5.97	)	$	(0.29	)	$	(0.22	)	$	(0.19	)





(1)	See Note 5 to the Consolidated Financial Statements for a description of changes in estimates related to warranty expense in 2013 and 2012.

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2013
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The accompanying consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of the Company’s consolidated financial statements in conformity with accounting principles generally accepted in the United States of America 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. 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.
Risks and Uncertainties	Risks and Uncertainties The Company is subject to risks inherent in a business with a limited operating history, including, but not limited to, new and rapidly evolving markets, advances and trends in the development of new technology and services, unfavorable economic and market conditions, competition from larger and more established companies, limited management resources and dependence on a limited number of contract manufacturers and suppliers. The inability to anticipate or to respond adequately to technological developments in the Company's industry, changes in customer or supplier requirements, or changes in regulatory requirements or industry standards could have a material adverse effect on the Company's business and operating results.
Revenue Recognition	Revenue Recognition The Company generates revenue from sales of its microinverter systems, which include microinverter units and related accessories, an Envoy communications gateway device, and an Enlighten web-based monitoring service, to distributors, large installers, OEMs and strategic partners. Enlighten service revenue represented less than 1% of the total revenues for all periods presented. Revenues from sales of microinverters and related accessories, and communication gateways are recognized when: (i) persuasive evidence of an arrangement exists; (ii) delivery of the products has occurred in accordance with the terms of the sales agreement and title of and risk of loss have passed to the customer; (iii) the sale price is fixed or determinable; and (iv) collection is reasonably assured. Provisions for rebates, sales incentives, and discounts to customers are accounted for as reductions in revenue in the same period the related sales are recorded. Sales of an Envoy communications gateway device include the Enlighten web-based monitoring service. The allocation of revenue between the two deliverables is based on the Company's best estimate of selling price determined by considering multiple factors including, internal costs, gross margin and historical pricing practices. After allocating the overall consideration from such sale to each deliverable using a best estimate of the selling price, (i) revenue from the sale of Envoy devices is recognized upon shipment, assuming all other revenue recognition criteria have been met and (ii) revenue from the web-based monitoring service is recognized ratably over the estimated economic life of the related Envoy devices of 10 years. Deferred revenues consist of payments received from customers in advance of revenue recognition for the Company’s products and services described above. As of December 31, 2013 and 2012, deferred revenues consist entirely of service revenue.
Cost of Revenues	Cost of Revenues The Company includes the following in cost of revenues: product costs, warranty, manufacturing personnel and logistics costs, inventory write-downs, hosting services costs related to the Company’s Enlighten service offering, and depreciation and amortization of manufacturing test equipment.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments, such as certificates of deposit and money market instruments with maturities of three months or less at the time of acquisition to be cash equivalents. For all periods presented, its cash balances consist of amounts held in non-interest-bearing deposits and money market accounts.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts of cash and cash equivalents, accounts receivable and accounts payable approximate fair value due to their relatively short-term nature. The carrying values of the Company's variable rate term loans approximate fair value.
Derivatives Instruments	Derivative Instruments The Company operates and conducts business in foreign countries where its foreign entities use the local currency as their respective functional currency. As a result, the Company is exposed to movements in foreign currency exchange rates. The Company utilizes foreign currency forward contracts to reduce the impact of foreign currency fluctuations related to anticipated cash receipts from expected future revenues denominated in Euros and intercompany transaction gains or losses. The foreign currency forward contracts are accounted for as derivatives whereby the fair value of the contracts is reported as other current assets or current liabilities in the accompanying consolidated balance sheets, and gains and losses resulting from changes in the fair value are reported in other income (expense), net, in the accompanying consolidated statements of operations.
Allowances for Doubtful Accounts	Allowances for Doubtful Accounts The Company maintains allowances for doubtful accounts for uncollectible accounts receivable. Management estimates anticipated losses from doubtful accounts based on days past due, collection history and the financial health of customers. The allowance for doubtful accounts was $2.0 million and $1.2 million at December 31, 2013 and 2012, respectively.
Inventory	Inventory Inventory is valued at the lower of cost or market. The Company determines cost on a first-in first-out basis. Certain factors could affect the realizable value of its inventory, including customer demand and market conditions. Management assesses the valuation on a quarterly basis and writes down the value for any excess and obsolete inventory based upon expected demand, anticipated sales price, effect of new product introductions, product obsolescence, customer concentrations, product merchantability and other factors. Inventory write-downs are equal to the difference between the cost of inventories and their estimated net realizable market value.
Property and Equipment	Property and Equipment Property and equipment are stated at cost less accumulated depreciation. Cost includes the price paid to acquire or construct the asset as well as any expenditure that substantially adds to the value of or significantly extends the useful life of an existing asset. Repair and maintenance costs are expensed as incurred. Depreciation and amortization is computed using the straight-line method over the estimated useful lives of the assets, which range from three to ten years. Leasehold improvements are amortized over the shorter of the lease term or expected useful life of the improvements.
Capitalized Software Costs	Capitalized Software Costs Internally used software, whether purchased or developed, is capitalized and amortized on a straight-line basis over their estimated useful lives. Costs associated with internally developed software are expensed until the point at which the project has reached the development stage. Subsequent additions, modifications or upgrades to internal-use software are capitalized only to the extent that they provide additional functionality. Software maintenance and training costs are expensed in the period in which they are incurred. The capitalization of software requires judgment in determining when a project has reached the development stage and the period over which the Company expects to benefit from the use of that software.
Long-Lived Assets	Long-Lived Assets Management evaluates long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to future undiscounted net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets.
Warranty Obligations	Warranty Obligations Microinverters Sold Through December 31, 2013 The Company’s warranty accrual provides for the replacement of microinverter units that fail during the product’s warranty term (15 years for first and second generation microinverters and up to 25 years for third and fourth generation microinverters). On a quarterly basis, the Company employs a consistent, systematic and rational methodology to assess the adequacy of its warranty liability. This assessment includes updating all key estimates and assumptions for each generation of product, based on historical results, trends and the most current data available as of the filing date. The key estimates and assumptions used in the warranty liability are thoroughly reviewed by management on a quarterly basis. The key estimates used by the Company to estimate its warranty liability are: (1) the number of units expected to fail over time (i.e. failure rate); (2) the number of failed units expected to result in warranty claims over time (i.e. claim rate); and (3) the per unit cost of replacement units, including outbound shipping and limited labor costs, expected to be incurred to replace failed units over time (i.e. replacement cost). Estimated Failure Rates—The Company’s Quality and Reliability department has primary responsibility to determine the estimated failure rates for each generation of microinverter. To establish initial failure rate estimates for each generation of microinverter, the Company’s quality engineers use a combination of industry standard MTBF (Mean Time Between Failure) estimates for individual components contained in its microinverters, third party data collected on similar equipment deployed in outdoor environments similar to those in which the Company’s microinverters are installed, and rigorous long term reliability and accelerated life cycle testing which simulates the service life of the microinverter in a short period of time. As units are deployed into production environments, the Company continues to monitor product performance via its Enlighten monitoring platform. It typically takes three to nine months between the date of sale and date of end-user installation. Consequently, the Company’s ability to monitor actual failures of units sold similarly lags by three to nine months. When a microinverter fails and is returned, the Company performs diagnostic root cause failure analysis to understand and isolate the underlying mechanism(s) causing the failure. The Company then uses the results of this analysis (combined with the actual, cumulative performance data collected on those units prior to failure via Enlighten) to draw conclusions with respect to how or if the identified failure mechanism(s) will impact the remaining units deployed in the installed base. Estimated Claim Rates—Warranty claim rate estimates are based upon assumptions with respect to expected customer behavior over the warranty period. As the vast majority of the Company’s microinverters have been sold to end users for residential applications, the Company believes that warranty claim rates will be affected by changes over time in residential home ownership because the Company expects that subsequent homeowners are less likely to file claims than the homeowners who originally purchase the microinverters. Estimated Replacement Costs—Three factors are considered in the Company’s analysis of estimated replacement cost: (1) the estimated cost of replacement microinverters; (2) the estimated cost to ship replacement microinverters to end users; and (3) the estimated labor reimbursement expected to be paid to third party installers performing replacement services for the end user. Because the Company’s warranty provides for the replacement of defective microinverters over long periods of time (either 15 or 25 years, depending on the generation of product purchased), the estimated per unit cost of current and future product generations is considered in the estimated replacement cost. Estimated costs to ship replacement units are based on observable, market-based shipping costs paid by the Company to third party freight carriers. The Company has a separate program that allows third-party installers to claim fixed-dollar reimbursements for labor costs they incur to replace failed microinverter units for a limited time from the date of original installation. Included in the Company’s estimated replacement cost is an analysis of the number of fixed-dollar labor reimbursements expected to be claimed by third party installers over the limited offering period. If actual failure rates, claim rates, or replacement costs differ from the Company’s estimates in future periods, changes to these estimates would be required, resulting in increases or decreases in the Company’s warranty obligations. Such increases or decreases could be material. Fair Value Option for Microinverters Sold Since January 1, 2014 The Company’s warranty obligations related to microinverters sold since January 1, 2014 provide the Company the right, but not the requirement, to assign its warranty obligations to a third-party. Pursuant to Accounting Standards Codification ("ASC") 820, Fair Value Measurement, such warranties are eligible to be accounted for at fair value. The Company expects to elect the fair value option to measure all eligible microinverter warranties for microinverters sold subsequent to January 1, 2014. In addition to the key estimates of failure rates, claim rates and replacement costs described above, the fair value of warranty obligations will require the use of certain Level 3 inputs which are unobservable and significant to the overall fair value measurement. Such additional assumptions will include a discount rate based upon the Company's credit-adjusted risk-free rate and a hypothetical profit margin and risk premium required of a hypothetical market participant to assume the obligation. Warranty obligations initially recorded at fair value (computed using an expected present value technique) at the time of sale will be subsequently re-measured to fair value at each reporting date. In addition, the fair value of the liability will be accreted over the corresponding term of the warranty of up to 25 years using the effective interest method. Any changes in fair value of the liability from period-to-period, including accretion expense, will be recognized in cost of revenues. If actual failure rates, claim rates, replacement costs, discount rate or the other additional assumptions differ from the Company’s estimates in future periods, changes to these estimates would be required, resulting in increases or decreases in the Company’s warranty obligations. Such increases or decreases could be material. As of December 31, 2013, warranty obligations were $30.4 million. Periodic adjustments necessitated by actual experience of claims and any future changes in estimates to this liability associated with sales prior to December 31, 2013 will continue to be accounted for on an undiscounted basis.
Research and Development Costs	Research and Development Costs The Company expenses research and development costs as incurred. Research and development costs totaled $34.5 million, $35.6 million and $25.1 million in 2013, 2012 and 2011, respectively.
Share-Based Compensation	Stock-Based Compensation Share-based payments are required to be recognized in the Company’s consolidated statements of operations based on their fair values and the estimated number of shares expected to vest. The Company measures stock-based compensation expense for all share-based payment awards, including stock options made to employees and directors, based on the estimated fair values on the date of the grant. The fair value of stock options granted is estimated using the Black-Scholes option valuation model. The fair value of restricted stock units granted is determined based on the price of the Company's common stock on the date of grant. Stock-based compensation, net of estimated forfeitures, is recognized on a straight-line basis over the requisite service period, which is typically four years.
Comprehensive Loss	Comprehensive Loss Comprehensive loss consists of two components, net loss and other comprehensive income (loss). Other comprehensive income (loss) refers to gains and losses that are recorded as an element of stockholders’ equity but are excluded from net income. The Company’s other comprehensive income (loss) consists of foreign currency translation adjustments for all periods presented.
Income Taxes	Income Taxes The Company records income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected tax consequences of temporary differences between the tax bases of assets and liabilities for financial reporting purposes and amounts recognized for income tax purposes. In estimating future tax consequences, generally all expected future events other than enactments or changes in the tax law or rates are considered. Valuation allowances are provided when necessary to reduce deferred tax assets to the amount expected to be realized. The Company operates in various tax jurisdictions and is subject to audit by various tax authorities. The Company follows accounting for uncertainty in income taxes which requires that the tax effects of a position be recognized only if it is “more likely than not” to be sustained based solely on its technical merits as of the reporting date. The Company considers many factors when evaluating and estimating its tax positions and tax benefits, which may require periodic adjustments and which may not accurately anticipate actual outcomes.

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2013

Accounting Policies [Abstract]

Schedule of changes in allowance for doubtful accounts

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



	December 31,
	2013		2012			2011
Balance, at beginning of year	$	1,177	$	144		$	17
Charged to expenses	678		1,068			127
Charged to Other Accounts	145		(35		)	—
Balance, at end of year	$	2,000	$	1,177		$	144

Inventory (Tables)

12 Months Ended

Dec. 31, 2013

Inventory Disclosure [Abstract]

Schedule of inventory

Inventory as of December 31, 2013 and 2012, consists of the following (in thousands):



	December 31,
	2013		2012
Raw materials	$	1,428	$	2,223
Finished goods	15,152		17,620
Total inventory	$	16,580	$	19,843

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2013

Property, Plant and Equipment [Abstract]

Property, plant and equipment

As of December 31, 2013 and 2012, property and equipment, net consists of the following (in thousands):



	Estimated Useful Life (Years)	December 31,
	Estimated Useful Life (Years)	2013			2012
Equipment and machinery	5	$	21,853		$	18,723
Furniture and fixtures	5–7	2,837			2,788
Computer equipment	3	1,842			1,688
Capitalized software	3–5	7,343			5,760
Leasehold improvements	3–10	5,881			5,642
Construction in progress		1,703			1,419
Total		41,459			36,020
Less accumulated depreciation and amortization		(16,606		)	(10,479		)
Property and equipment, net		$	24,853		$	25,541

The following table summarizes capitalized internal-use software costs (in thousands):



	December 31, 2013				December 31, 2012
	Gross Cost		Net of Accumulated Amortization		Gross Cost		Net of Accumulated Amortization
Developed internal-use software	$	3,322	$	1,333	$	2,570	$	1,053
Purchased software for internal use	4,021		2,311		3,190		2,227
Total software	$	7,343	$	3,644	$	5,760	$	3,280

Warranty Obligations (Tables)

12 Months Ended

Dec. 31, 2013

Product Warranties Disclosures [Abstract]

Changes in the Company's product warranty liability

The Company’s warranty activities during 2013, 2012 and 2011 were as follows (in thousands):



	December 31,
	2013			2012			2011
Balance, at beginning of year	$	21,338		8,738			$	2,668
Accruals for warranties issued during the year	6,303			8,218			5,279
Changes in estimates	10,303			7,607			1,751
Settlements	(7,512		)	(3,225		)	(960		)
Balance, at end of year	30,432			21,338			8,738
Less current portion included in accrued liabilities	(4,942		)	(6,078		)	(2,005		)
Long-term portion	$	25,490		$	15,260		$	6,733

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2013

Fair Value Disclosures [Abstract]

Schedule of financial instruments that are measured at fair value on a recurring basis



	Asset Derivatives				Liability Derivatives
	December 31, 2013		December 31, 2012		December 31, 2013		December 31, 2012
Foreign currency forward contracts (Level 2)	$	325	$	—	$	605	$	268

Long-Term Debt (Tables)

12 Months Ended

Dec. 31, 2013

Debt Disclosure [Abstract]

Schedule of long-term debt

The Company’s long-term debt was comprised of the following at December 31, 2013 and 2012 (in thousands):



	December 31,
	2013			2012
Term loans	$	7,400		$	7,400
Equipment financing facility, net of unamortized discount of $31 and $94, respectively	1,277			3,661
Total debt	8,677			11,061
Less current portion	(3,507		)	(2,384		)
Long-term portion	$	5,170		$	8,677

Schedule of maturities of long-term debt

As of December 31, 2013, the amount of future principal repayments due on the total debt is as follows (in thousands):



2014	$	3,538
2015	2,973
2016	2,197
Total	$	8,708

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6584090&loc=d3e28878-108400

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21538-112644

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28541-108399

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21521-112644

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 22
-Article 5

+ Details

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2013

Commitments and Contingencies Disclosure [Abstract]

Schedule of future minimum rental payments for operating leases

The Company’s minimum lease payments under noncancelable operating leases, exclusive of executory costs, as of December 31, 2013 are as follows (in thousands):



2014	$	1,672
2015	1,749
2016	1,766
2017	1,555
2018	1,599
Thereafter	5,756
Total minimum lease payments	$	14,097

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2013

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

Schedule of valuation assumptions of stock options

The assumptions used in calculating fair values for stock options granted under the Plan and the resultant weighted-average estimated fair values for the periods presented are as follows:



	Year Ended December 31,
	2013			2012			2011
Expected term (in years)	4.4			5.7			6.0
Expected volatility	68.4		%	74.5		%	72.0		%
Annual risk-free rate of return	1.0		%	0.9		%	1.8		%
Dividend yield	—		%	—		%	—		%
Weighted-average fair value on grant date	$	3.84		$	4.69		$	5.08

Schedule of components of stock-based compensation expense in the consolidated statement of operations, by report line

The following table summarizes the components of total stock-based compensation expense included in the consolidated statement of operations for the periods presented (in thousands):



	Year Ended December 31,
	2013		2012		2011
Cost of revenues	$	438	$	196	$	39
Research and development	2,110		1,728		795
Sales and marketing	1,812		1,254		671
General and administrative	2,489		1,588		615
Total stock-based compensation expense	$	6,849	$	4,766	$	2,120

Schedule of stock-based compensation expense by award type

The following table summarizes stock-based compensation associated with each type of award:



	Year Ended December 31,
	2013		2012		2011
Stock options and restricted stock units	$	6,314	$	4,519	$	2,120
ESPP	535		247		—
Total stock-based compensation expense	$	6,849	4,766		$	2,120

Schedule of summary of stock option activity

A summary of the Company’s stock option activity for 2013, 2012 and 2011 is as follows (in thousands, except per share data):



	Shares		Weighted- Average Exercise Price per Share
Options outstanding — December 31, 2010	5,802		$	0.90
Granted	1,110		6.16
Exercised	(502	)	0.38
Canceled	(154	)	2.82
Options outstanding — December 31, 2011	6,256		1.83
Granted	2,478		7.35
Exercised	(59	)	1.26
Canceled	(506	)	5.55
Options outstanding — December 31, 2012	8,169		3.28
Granted	1,506		7.17
Exercised	(822	)	1.69
Canceled	(344	)	7.74
Options outstanding — December 31, 2013	8,509		3.94

Schedule of stock options outstanding under the 2006 and 2011 Plans

The following table summarizes information about stock options outstanding at December 31, 2013:



	Options Outstanding				Options Exercisable
Range of Exercise Prices	Number of Shares (in thousands)	Weighted- Average Remaining Life (in years)	Weighted- Average Exercise Price		Number of Shares (in thousands)	Weighted- Average Exercise Price
$0.27 —– $0.91	2,424	5.5	$	0.29	2,424	$	0.29
$1.63 —– $1.63	1,663	6.5	1.63		1,486	1.63
$2.00 —– $5.78	1,209	6.3	3.87		617	3.32
$5.87 —– $7.50	1,379	7.4	6.91		428	7.00
$7.68 —– $8.82	1,280	7.3	8.09		309	8.26
$9.40 —– $11.00	554	7.7	10.04		287	9.98
Total	8,509	6.6	3.94		5,551	2.45

Schedule of restricted stock unit activity

The following is a summary of restricted stock unit activity for 2013 and 2012 (in thousands, except per share data):



	Restricted Stock Units		Weighted Average Fair Value per Share at Grant Date
Outstanding at December 31, 2011	—		$	—
Granted	282		5.69
Vested	(20	)	2.00
Canceled	(14	)	6.90
Outstanding at December 31, 2012	248		5.53
Granted	285		6.92
Vested	(107	)	6.08
Canceled	(8	)	7.07
Outstanding at December 31, 2013	418		6.31

Schedule of summary of ESPP

The following is a summary of ESPP activity for 2013 and 2012 and (in thousands, except per share data):



	Year Ended December 31,
	2013		2012
Proceeds from common stock issued under ESPP	$	1,047	$	185
Shares of common stock issued	327		59
Weighted-average price per share	$	3.20	$	3.14

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2013

Income Tax Disclosure [Abstract]

Schedule of Effective Income Tax Rate Reconciliation



	Year Ended December 31,
	2013			2012			2011
Income tax benefit at statutory rate	$	(8,517	)	$	(12,773	)	$	(10,883	)
State taxes, net of federal benefit	(883		)	(1,478		)	(1,956		)
Change in valuation allowance	8,353			12,574			12,451
Stock-based compensation	1,191			1,128			479
Other	455			1,027			(91		)
Uncertain tax positions	264			173			—
Provision for income taxes	$	863		$	651		$	—

Schedule of Deferred Tax Assets and Liabilities

A summary of significant components of the Company’s deferred tax assets and liabilities as of December 31, 2013 and 2012 is as follows (in thousands):



	December 31,
	2013			2012
Current:
Reserves and allowances	$	14,521		$	11,523
Valuation allowance	(14,521		)	(11,523		)
Total current	—			—
Non-current:
Net operating losses	16,840			14,364
Stock-based compensation	1,531			919
Deferred revenue	2,730			1,425
Fixed assets and intangibles	11,670			10,301
Other	476			880
Valuation allowance	(33,245		)	(27,889		)
Total non-current	2			—
Deferred tax liability	—			—
Net deferred tax assets	$	2		$	—

Net Loss Per Share Attributable to Common Stockholders (Tables)

12 Months Ended

Dec. 31, 2013

Earnings Per Share [Abstract]

Schedule of potential common shares outstanding that were excluded from the computation of diluted net loss per share attributable to common stockholders



	Year Ended December 31,
	2013	2012	2011
Convertible preferred stock	—	—	25,171
Stock options to purchase common stock	8,196	8,174	6,256
Convertible notes	—	—	2,328
Unvested restricted stock units	381	248	—
Warrants to purchase common stock	308	331	143
Convertible preferred stock warrants	—	—	215
Total	8,885	8,753	34,113

Segment and Geographic Information (Tables)

12 Months Ended

Dec. 31, 2013

Segment Reporting [Abstract]

Net revenues and long-lived assets by geographic region

Long-Lived Assets



	As of December 31,
	2013		2012		2011
United States	$	16,262	$	17,136	$	11,199
China	7,130		6,642		5,974
Other	1,461		1,763		1,238
Total	$	24,853	$	25,541	$	18,411

Net Revenues



	Year Ended December 31,
	2013		2012		2011
United States	$	192,881	$	189,711	$	128,692
International	39,965		26,967		20,831
Total	$	232,846	$	216,678	$	149,523

Quarterly Financial Information (Tables)

12 Months Ended

Dec. 31, 2013

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information

Quarterly Financial Information

(Unaudited)

(In thousands, except per share data)



	Quarters Ended for Fiscal 2013
	March 31			June 30			September 30			December 31

Net revenues	$	45,577		$	58,167		$	62,046		$	67,056
Cost of revenues⁽¹⁾	33,376			41,883			44,611			45,560
Gross profit	12,201			16,284			17,435			21,496
Operating expenses:
Research and development	9,026			8,484			8,293			8,721
Sales and marketing	6,850			7,365			8,550			8,315
General and administrative	6,036			5,926			5,937			6,071
Total operating expenses	21,912			21,775			22,780			23,107
Loss from operations	(9,711		)	(5,491		)	(5,345		)	(1,611		)
Other expense, net	(513		)	(781		)	(815		)	(783		)
Loss before income taxes	(10,224		)	(6,272		)	(6,160		)	(2,394		)
Provision for income taxes	(182		)	(124		)	(141		)	(416		)
Net loss	$	(10,406	)	$	(6,396	)	$	(6,301	)	$	(2,810	)
Net loss per share, basic and diluted	$	(0.25	)	$	(0.15	)	$	(0.15	)	$	(0.07	)

	Quarters Ended for Fiscal 2012
	March 31			June 30			September 30			December 31
Net revenues	$	42,600		$	55,697		$	60,813		$	57,568
Cost of revenues⁽¹⁾	33,293			42,096			44,489			41,512
Gross profit	9,307			13,601			16,324			16,056
Operating expenses:
Research and development	7,842			8,655			10,571			8,533
Sales and marketing	5,049			6,360			7,039			7,525
General and administrative	5,696			6,091			6,911			6,177
Total operating expenses	18,587			21,106			24,521			22,235
Loss from operations	(9,280		)	(7,505		)	(8,197		)	(6,179		)
Other expense, net	(839		)	(3,729		)	(580		)	(1,258		)
Loss before income taxes	(10,119		)	(11,234		)	(8,777		)	(7,437		)
Provision for income taxes	(65		)	(151		)	(130		)	(305		)
Net loss	$	(10,184	)	$	(11,385	)	$	(8,907	)	$	(7,742	)
Net loss per share, basic and diluted	$	(5.97	)	$	(0.29	)	$	(0.22	)	$	(0.19	)





(1)	See Note 5 to the Consolidated Financial Statements for a description of changes in estimates related to warranty expense in 2013 and 2012.

Summary of Significant Accounting Policies ( Activities in the Allowance for Doubtful Accounts) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, at beginning of year	$ 1,177	$ 144	$ 17
Charged to expenses	678	1,068	127
Charged to Other Accounts	145	(35)	0
Balance, at end of year	$ 2,000	$ 1,177	$ 144

Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accounting Policies [Line Items]
Allowance for doubtful accounts	$ 2,000				$ 1,177				$ 2,000	$ 1,177	$ 144	$ 17
Warranty obligation	30,432				21,338				30,432	21,338	8,738	$ 2,668
Research and development expense	$ 8,721	$ 8,293	$ 8,484	$ 9,026	$ 8,533	$ 10,571	$ 8,655	$ 7,842	$ 34,524	$ 35,601	$ 25,099
Stock-based compensation requisite service period									4 years
First and Second Generation
Accounting Policies [Line Items]
Product warranty, term									15 years
Minimum
Accounting Policies [Line Items]
Property and equipment estimated useful life									3 years
Product warranty, term									15 years
Product installation period									3 months
Period failure rate measurement lags product sale									3 months
Maximum
Accounting Policies [Line Items]
Property and equipment estimated useful life									10 years
Product warranty, term									25 years
Product installation period									9 months
Period failure rate measurement lags product sale									9 months
Maximum \| Third and Fourth Generation
Accounting Policies [Line Items]
Product warranty, term									25 years
Maximum \| Enlighten
Accounting Policies [Line Items]
Percent of revenue represented by product line or service									1.00%
Revenue recognition period									10 years

Inventory (Summary of Inventory) (Details) - USD ($)	12 Months Ended
Inventory (Summary of Inventory) (Details) - USD ($)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Schedule of inventory
Raw materials	$ 1,428,000	$ 2,223,000
Finished goods	15,152,000	17,620,000
Total inventory	16,580,000	19,843,000
Inventory (Textual) [Abstract]
Inventory write-downs	$ 0	$ 800,000	$ 2,700,000

Property and Equipment, Net (Summary of Property and Equipment , Net) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 41,459	$ 36,020
Less accumulated depreciation and amortization	(16,606)	(10,479)
Property and equipment, net	24,853	25,541
Depreciation and amortization	$ 5,500	4,400	$ 2,300
Equipment and machinery
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Property and equipment, gross	$ 21,853	18,723
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 2,837	2,788
Computer equipment
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Property and equipment, gross	$ 1,842	1,688
Capitalized software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	7,343	5,760
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	5,881	5,642
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,703	$ 1,419
Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Minimum \| Furniture and fixtures
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Minimum \| Capitalized software
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Minimum \| Leasehold improvements
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	10 years
Maximum \| Furniture and fixtures
Property, Plant and Equipment [Line Items]
Estimated useful life	7 years
Maximum \| Capitalized software
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Maximum \| Leasehold improvements
Property, Plant and Equipment [Line Items]
Estimated useful life	10 years

Property and Equipment, Net (Capitalized Software Costs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Property, Plant and Equipment [Line Items]
Amortization of capitalized internal use computer software	$ 1,500	$ 1,200	$ 700
Capitalized Computer Software
Gross Cost	7,343	5,760
Net of Accumulated Amortization	3,644	3,280
Internal-use software
Capitalized Computer Software, Future Amortization Expense
2014	1,700
2015	1,200
2016	700
Developed internal-use software
Capitalized Computer Software
Gross Cost	3,322	2,570
Net of Accumulated Amortization	1,333	1,053
Purchased software for internal use
Capitalized Computer Software
Gross Cost	4,021	3,190
Net of Accumulated Amortization	$ 2,311	$ 2,227

Warranty Obligations (Summary of Warranty Obligations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Changes in the Company's product warranty liability
Balance, at beginning of year	$ 21,338	$ 8,738	$ 2,668
Accruals for warranties issued during the year	6,303	8,218	5,279
Changes in estimates	10,303	7,607	1,751
Settlements	(7,512)	(3,225)	(960)
Balance, at end of year	30,432	21,338	8,738
Less current portion included in accrued liabilities	(4,942)	(6,078)	(2,005)
Long-term portion	$ 25,490	$ 15,260	$ 6,733

Warranty Obligations (Narrative) (Details) unit in Thousands, $ in Millions	3 Months Ended			6 Months Ended	12 Months Ended			18 Months Ended	42 Months Ended
	Dec. 31, 2013 USD ($)	Sep. 30, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2013 unit	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2013 unit	Jun. 30, 2012 unit
Minimum
Product Liability Contingency [Line Items]
Product warranty, term					15 years
Maximum
Product Liability Contingency [Line Items]
Product warranty, term					25 years
Replacement cost
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in warranty variables estimates						$ (2.1)
Claim rate
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in warranty variables estimates						(0.5)
Shipping cost
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in warranty variables estimates						(1.9)
Second Generation
Product Liability Contingency [Line Items]
Number of units sold \| unit									1,000
Second Generation \| Failure rate
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in warranty variables estimates	$ 3.5		$ 2.4		$ 19.5	$ 10.2
Second Generation \| Replacement cost
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in warranty variables estimates							$ 1.8
Third Generation
Product Liability Contingency [Line Items]
Number of units sold \| unit								3,500
Third Generation \| Failure rate
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in warranty variables estimates		$ (3.1)
Fourth Generation
Product Liability Contingency [Line Items]
Number of units sold \| unit				150
Fourth Generation \| Replacement cost
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in warranty variables estimates	$ (1.7)				$ (1.9)
Second and Third Generation \| Minimum
Product Liability Contingency [Line Items]
Product warranty, term					15 years
Second and Third Generation \| Maximum
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in warranty variables estimates					$ (4.2)
Product warranty, term					25 years
Enlighten \| Minimum
Product Liability Contingency [Line Items]
Percent of end user customers using performance tracking system			80.00%
Enlighten \| Maximum
Product Liability Contingency [Line Items]
Percent of end user customers using performance tracking system			90.00%

Fair Value Measurements (Details) - Recurring - Level 2 - USD ($) $ in Thousands	Dec. 31, 2013	Dec. 31, 2012
Asset Derivatives
Foreign currency forward contracts (Level 2)	$ 325	$ 0
Liability Derivatives
Foreign currency forward contracts (Level 2)	$ 605	$ 268

Fair Value Measurements (Narrative) (Details) - Not designated as hedging instrument - Foreign exchange forward - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Derivative [Line Items]
Notional amount of foreign currency	$ 12.5	$ 6.1
Net loss on foreign currency	$ 0.4	$ 0.5

Long-Term Debt (Schedule of Debt) (Details) - USD ($) $ in Thousands	Dec. 31, 2013	Dec. 31, 2012
Schedule of long-term debt
Total debt	$ 8,677	$ 11,061
Less current portion	(3,507)	(2,384)
Long-term portion	5,170	8,677
Term loans
Schedule of long-term debt
Total debt	7,400	7,400
Equipment financing facility, net of unamortized discount of $31 and $94, respectively
Schedule of long-term debt
Total debt	1,277	3,661
Net of unamortized discount	$ 31	$ 94

Long-Term Debt (Schedule of Maturities) (Details) $ in Thousands	Dec. 31, 2013 USD ($)
Debt Disclosure [Abstract]
2014	$ 3,538
2015	2,973
2016	2,197
Total	$ 8,708

Long-Term Debt (Narrative) (Details)	12 Months Ended
Long-Term Debt (Narrative) (Details)	Dec. 31, 2013 USD ($)
Long-Term Debt (Textual) [Abstract]
Long-term debt, gross	$ 8,708,000
Revolving Credit Facility \| Wells Fargo Bank
Long-Term Debt (Textual) [Abstract]
Convertible loan facility, maximum borrowing capacity	50,000,000.0
Amount of liquidity required for debt compliance	15,000,000.0
Amount of undrawn credit for debt compliance	8,000,000.0
Amount of liquidity required for debt compliance	5,000,000.0
Convertible loan facility, remaining borrowing capacity	$ 22,400,000
Revolving Credit Facility \| Wells Fargo Bank \| Minimum \| LIBOR or Base Rate
Long-Term Debt (Textual) [Abstract]
Term Loan interest at an prime rate	1.50%
Revolving Credit Facility \| Wells Fargo Bank \| Maximum \| LIBOR or Base Rate
Long-Term Debt (Textual) [Abstract]
Term Loan interest at an prime rate	4.25%
Term loan \| Hercules Technology Growth Capital, Inc
Long-Term Debt (Textual) [Abstract]
Convertible loan facility, maximum borrowing capacity	$ 7,400,000
Debt instrument additional borrowing amount	$ 15,600,000
Term Loan interest at an annual rate	11.50%
Credit facility, end of term charge	$ 600,000
Long-term debt, gross	$ 7,400,000
Term loan \| Hercules Technology Growth Capital, Inc \| Prime Rate
Long-Term Debt (Textual) [Abstract]
Term Loan interest at an prime rate	8.25%
Term loan \| Horizon Technology Finance Corporation
Long-Term Debt (Textual) [Abstract]
Repayment of term loans	$ 7,500,000
Equipment financing facility \| Hercules Technology Growth Capital, Inc
Long-Term Debt (Textual) [Abstract]
Term Loan interest at an annual rate	9.00%
Long-term debt, gross	$ 1,300,000
Equipment financing facility \| Hercules Technology Growth Capital, Inc \| Prime Rate
Long-Term Debt (Textual) [Abstract]
Term Loan interest at an prime rate	5.75%

Commitments and Contingencies (Future Minimum Payments for Operating Leases) (Details) $ in Thousands	Dec. 31, 2013 USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2014	$ 1,672
2015	1,749
2016	1,766
2017	1,555
2018	1,599
Thereafter	5,756
Total minimum lease payments	$ 14,097

Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Commitments and Contingencies [Line Items]
Rent expense	$ 2.6	$ 2.4	$ 1.2
Purchase obligation	87.6
Cancelable portion of purchase obligation	72.5
Purchase obligation cancellation penalties	$ 5.6
Maximum
Commitments and Contingencies [Line Items]
Purchase obligation time period	7 years

Stockholders' Equity (Narrative) (Details) $ / shares in Units, $ in Thousands		12 Months Ended
	Apr. 04, 2012 USD ($) $ / shares shares	Dec. 31, 2013 USD ($) $ / Units shares	Dec. 31, 2012 USD ($) shares	Dec. 31, 2011 USD ($) $ / shares
Class of Stock [Line Items]
Common stock shares issued during period, in connection with credit facility (shares) \| shares	10,315,151
Common stock issued, price per share (usd per share) \| $ / shares	$ 6.00			$ 5.27
Net proceeds from IPO	$ 53,800	$ 0	$ 58,609	$ 0
Underwriter's discounts and commissions	3,300
Other estimated offering costs	$ 4,800
Convertible preferred stock, shares outstanding \| shares	22,220,856	0	0
Convertible preferred stock outstanding, value	$ 93,600
Convertible notes, outstanding balance of principal and accrued paid in kind interest	$ 21,200
Conversion of convertible preferred stock into common stock (shares) \| shares	25,171,017
Conversion of notes into common stock (shares) \| shares	3,533,988
Common stock conversion price per share (usd per share) \| $ / shares	$ 6.00
Debt interest expense			$ 2,800
Common Stock
Class of Stock [Line Items]
Number of securities called by warrants \| shares		293,474
Common Stock \| Minimum
Class of Stock [Line Items]
Warrant to purchase common stock, price per share (usd per share) \| $ / Units		5.27
Common Stock \| Maximum
Class of Stock [Line Items]
Warrant to purchase common stock, price per share (usd per share) \| $ / Units		6.17

Stock-Based Compensation (Valuation Assumptions of Stock Options Under Black-Scholes Model) (Details) - Stock options - $ / shares	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
The Fair Value of Each Option Granted During the Period [Abstract]
Expected term (in years)	4 years 4 months 24 days	5 years 8 months 12 days	6 years
Expected volatility	68.40%	74.50%	72.00%
Annual risk-free rate of return	1.00%	0.90%	1.80%
Dividend yield	0.00%	0.00%	0.00%
Weighted-average fair value on grant date (usd per share)	$ 3.84	$ 4.69	$ 5.08

Stock-Based Compensation (Components of Stock-based Compensation Expense by Report Line) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Allocation of Stock-based Compensation Expense Included in the Consolidated Statement of Operations [Abstract]
Total stock-based compensation expense	$ 6,849	$ 4,766	$ 2,120
Cost of revenues
Allocation of Stock-based Compensation Expense Included in the Consolidated Statement of Operations [Abstract]
Total stock-based compensation expense	438	196	39
Research and development
Allocation of Stock-based Compensation Expense Included in the Consolidated Statement of Operations [Abstract]
Total stock-based compensation expense	2,110	1,728	795
Sales and marketing
Allocation of Stock-based Compensation Expense Included in the Consolidated Statement of Operations [Abstract]
Total stock-based compensation expense	1,812	1,254	671
General and administrative
Allocation of Stock-based Compensation Expense Included in the Consolidated Statement of Operations [Abstract]
Total stock-based compensation expense	$ 2,489	$ 1,588	$ 615

Stock-Based Compensation (Expense by Award Type) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 6,849	$ 4,766	$ 2,120
Stock options and restricted stock units
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	6,314	4,519	2,120
ESPP
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 535	$ 247	$ 0

Stock-Based Compensation (Stock Option Activity) (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Shares
Options outstanding, beginning (shares)	8,169	6,256	5,802
Granted (shares)	1,506	2,478	1,110
Exercised (shares)	(822)	(59)	(502)
Canceled (shares)	(344)	(506)	(154)
Options outstanding, ending (shares)	8,509	8,169	6,256
Weighted- Average Exercise Price per Share
Options outstanding, beginning (usd per share)	$ 3.28	$ 1.83	$ 0.90
Granted (usd per share)	7.17	7.35	6.16
Exercised (usd per share)	1.69	1.26	0.38
Canceled (usd per share)	7.74	5.55	2.82
Options outstanding, ending (usd per share)	$ 3.94	$ 3.28	$ 1.83

Stock-Based Compensation (Range of Exercise Price) (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2013 $ / shares shares
Exercise Price Range of Options Outstanding and Options Exercisable [Line Items]
Number of Shares Outstanding \| shares	8,509
Weighted- Average Remaining Life of Outstanding Options (in years)	6 years 7 months 6 days
Weighted- Average Exercise Price of Options Outstanding (usd per share)	$ 3.94
Number of Shares Exercisable \| shares	5,551
Weighted- Average Exercise Price of Options Exercisable (usd per share)	$ 2.45
$0.27 – $0.91
Exercise Price Range of Options Outstanding and Options Exercisable [Line Items]
Range of Exercise Prices - Lower Range Limit (usd per share)	0.27
Range of Exercise Prices - Upper Range Limit (usd per share)	$ 0.91
Number of Shares Outstanding \| shares	2,424
Weighted- Average Remaining Life of Outstanding Options (in years)	5 years 6 months
Weighted- Average Exercise Price of Options Outstanding (usd per share)	$ 0.29
Number of Shares Exercisable \| shares	2,424
Weighted- Average Exercise Price of Options Exercisable (usd per share)	$ 0.29
$1.63 - $1.63
Exercise Price Range of Options Outstanding and Options Exercisable [Line Items]
Range of Exercise Prices - Lower Range Limit (usd per share)	1.63
Range of Exercise Prices - Upper Range Limit (usd per share)	$ 1.63
Number of Shares Outstanding \| shares	1,663
Weighted- Average Remaining Life of Outstanding Options (in years)	6 years 6 months
Weighted- Average Exercise Price of Options Outstanding (usd per share)	$ 1.63
Number of Shares Exercisable \| shares	1,486
Weighted- Average Exercise Price of Options Exercisable (usd per share)	$ 1.63
$2.00 – $5.78
Exercise Price Range of Options Outstanding and Options Exercisable [Line Items]
Range of Exercise Prices - Lower Range Limit (usd per share)	2
Range of Exercise Prices - Upper Range Limit (usd per share)	$ 5.78
Number of Shares Outstanding \| shares	1,209
Weighted- Average Remaining Life of Outstanding Options (in years)	6 years 3 months 18 days
Weighted- Average Exercise Price of Options Outstanding (usd per share)	$ 3.87
Number of Shares Exercisable \| shares	617
Weighted- Average Exercise Price of Options Exercisable (usd per share)	$ 3.32
$5.87 - $7.50
Exercise Price Range of Options Outstanding and Options Exercisable [Line Items]
Range of Exercise Prices - Lower Range Limit (usd per share)	5.87
Range of Exercise Prices - Upper Range Limit (usd per share)	$ 7.50
Number of Shares Outstanding \| shares	1,379
Weighted- Average Remaining Life of Outstanding Options (in years)	7 years 4 months 24 days
Weighted- Average Exercise Price of Options Outstanding (usd per share)	$ 6.91
Number of Shares Exercisable \| shares	428
Weighted- Average Exercise Price of Options Exercisable (usd per share)	$ 7.00
$7.68 - $8.82
Exercise Price Range of Options Outstanding and Options Exercisable [Line Items]
Range of Exercise Prices - Lower Range Limit (usd per share)	7.68
Range of Exercise Prices - Upper Range Limit (usd per share)	$ 8.82
Number of Shares Outstanding \| shares	1,280
Weighted- Average Remaining Life of Outstanding Options (in years)	7 years 3 months 18 days
Weighted- Average Exercise Price of Options Outstanding (usd per share)	$ 8.09
Number of Shares Exercisable \| shares	309
Weighted- Average Exercise Price of Options Exercisable (usd per share)	$ 8.26
$9.40 - $11.00
Exercise Price Range of Options Outstanding and Options Exercisable [Line Items]
Range of Exercise Prices - Lower Range Limit (usd per share)	9.4
Range of Exercise Prices - Upper Range Limit (usd per share)	$ 11
Number of Shares Outstanding \| shares	554
Weighted- Average Remaining Life of Outstanding Options (in years)	7 years 8 months 12 days
Weighted- Average Exercise Price of Options Outstanding (usd per share)	$ 10.04
Number of Shares Exercisable \| shares	287
Weighted- Average Exercise Price of Options Exercisable (usd per share)	$ 9.98

Stock-Based Compensation (Restricted Stock Unit Activity) (Details) - Restricted stock units - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Restricted Stock Units
Outstanding units, beginning (shares)	248	0
Granted (shares)	285	282
Vested (shares)	(107)	(20)
Canceled (shares)	(8)	(14)
Outstanding units, ending (shares)	418	248
Weighted Average Fair Value per Share at Grant Date
Outstanding units, beginning (usd per share)	$ 5.53	$ 0.00
Granted (usd per share)	6.92	5.69
Vested (usd per share)	6.08	2.00
Canceled (usd per share)	7.07	6.90
Outstanding units, ending (usd per share)	$ 6.31	$ 5.53

Stock-Based Compensation (Summary of ESPP activity) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Proceeds from common stock issued under ESPP	$ 1,047	$ 185
Shares of common stock issued	327	59
Weighted-average price per share (usd per share)	$ 3.20	$ 3.14

Stock-Based Compensation (Narrative) (Details)		12 Months Ended
Stock-Based Compensation (Narrative) (Details)	Jan. 02, 2014 shares	Dec. 31, 2013 USD ($) purchase_period $ / shares shares	Dec. 31, 2012 USD ($) shares	Dec. 31, 2011 shares	Dec. 31, 2010 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares outstanding (shares)		8,509,000	8,169,000	6,256,000	5,802,000
Number of shares outstanding, granted (shares)		1,506,000	2,478,000	1,110,000
Total unrecognized compensation cost \| $		$ 13,200,000
Weighted-average period		2 years 7 months 6 days
Intrinsic value of options exercised \| $		$ 3,200,000	$ 300,000
Number of options outstanding that were vested and expected to vest		8,300,000
Weighted-average fair value, vested (in usd per share) \| $ / shares		$ 3.87
Weighted-average remaining contractual term, vested		6 years 6 months
Aggregate intrinsic value, exercisable shares \| $		$ 23,500,000
Number of shares exercisable		5,551,000
Common stock fair value (in usd per share) \| $ / shares		$ 6.34
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of units vested \| $		$ 800,000	$ 39,000
Weighted average remaining contractual term		1 year 7 months 6 days
Intrinsic value of restricted stock units outstanding \| $		$ 2,600,000
2006 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity awards granted period vest over		4 years
Common stock, shares outstanding (shares)		5,200,000
Number of shares outstanding, granted (shares)		0
2006 Plan \| Before August 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity awards granted contractual term		10 years
2011 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity awards granted period vest over		4 years
Issue of common stock (in shares)		2,643,171
Expiration term of ESPP		10 years
Increase in number of shares of common stock reserved for issuance under the stock incentive plan		4.50%
Maximum number of shares that be issued pursuant to the exercise of incentive stock options		586,524
2011 Plan \| Subsequent event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in shares authorized for issuance under plan	1,895,541
2011 Plan \| After August 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity awards granted contractual term		7 years
2011 Employee Stock Purchase Plan (ESPP)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issue of common stock (in shares)		669,603
Maximum number of shares that be issued pursuant to the exercise of incentive stock options		613,984
Yearly, share increase in reserved shares		330,396
Number of interim purchase periods \| purchase_period		4
General duration (in months) of employee stock purchase plan		24 months
Payroll deductions		15.00%
Fair market value		85.00%
Look-back feature in ESPP		2 years
Recognition period for additional expense triggered by the reset feature		24 months
Purchase of common stock \| $		$ 25,000
2011 Employee Stock Purchase Plan (ESPP) \| Subsequent event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Yearly, share increase in reserved shares	330,396

Income Taxes (Effective Income Tax Reconciliation) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Income tax benefit at statutory rate									$ (8,517)	$ (12,773)	$ (10,883)
State taxes, net of federal benefit									(883)	(1,478)	(1,956)
Change in valuation allowance									8,353	12,574	12,451
Stock-based compensation									1,191	1,128	479
Other									455	1,027	(91)
Uncertain tax positions									264	173	0
Provision for income taxes	$ 416	$ 141	$ 124	$ 182	$ 305	$ 130	$ 151	$ 65	$ 863	$ 651	$ 0

Income Taxes (Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2013	Dec. 31, 2012
Current:
Reserves and allowances	$ 14,521	$ 11,523
Valuation allowance	(14,521)	(11,523)
Total current	0	0
Non-current:
Net operating losses	16,840	14,364
Stock-based compensation	1,531	919
Deferred revenue	2,730	1,425
Fixed assets and intangibles	11,670	10,301
Other	476	880
Valuation allowance	(33,245)	(27,889)
Total non-current	2	0
Deferred tax liability	0	0
Net deferred tax assets	$ 2	$ 0

Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Taxes [Line Items]
Provision for income taxes related to foreign operations	$ 900	$ 700
Federal statutory income tax rate	34.00%	34.00%	34.00%
Net operating losses from excess stock option benefits	$ 201
Unrecognized tax benefits	376	$ 160
Unrecognized tax benefits, increases in tax positions for the current year	137
Unrecognized tax benefits, increases in tax positions for prior year	79
Unrecognized tax benefits, accrued interest and penalties	47
Internal Revenue Service (IRS)
Income Taxes [Line Items]
Operating loss carryforwards	61,300
California
Income Taxes [Line Items]
Operating loss carryforwards	$ 53,000

Concentration of Credit Risk and Major Customers (Narrative) (Details)	12 Months Ended
	Dec. 31, 2013 customer	Dec. 31, 2012 accounts_receivable customer	Dec. 31, 2011 customer
Accounts Receivable \| Credit Concentration Risk
Revenue, Major Customer [Line Items]
Number of customers considered to give rise to concentration risk	2	2
Net Revenue \| Customer Concentration Risk
Revenue, Major Customer [Line Items]
Number of customers considered to give rise to concentration risk	3	2	3
Customer Providing Largest Concentration of Receivable \| Accounts Receivable \| Credit Concentration Risk
Revenue, Major Customer [Line Items]
Percentage of concentration risk	16.00%	21.00%
Customer Providing Second Largest Concentration of Receivable \| Accounts Receivable \| Credit Concentration Risk
Revenue, Major Customer [Line Items]
Percentage of concentration risk	10.00%	16.00%
Customer Accounting for the Largest Concentration of Revenue \| Net Revenue \| Customer Concentration Risk
Revenue, Major Customer [Line Items]
Percentage of concentration risk	15.00%	16.00%	17.00%
Customer Accounting for Second Largest Concentration of Revenue \| Net Revenue \| Customer Concentration Risk
Revenue, Major Customer [Line Items]
Percentage of concentration risk	14.00%	11.00%	11.00%
Customer Accounting for Third Largest Concentraion \| Net Revenue \| Customer Concentration Risk
Revenue, Major Customer [Line Items]
Percentage of concentration risk	11.00%		10.00%

Net Loss Per Share Attributable to Common Stockholders (Potential Common Shares Outstanding Excluded from Computation of Diluted Net Loss Per Share) (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
The potential common shares outstanding that were excluded from the computation of diluted net loss per share attributable to common stockholders
Total	8,885	8,753	34,113
Convertible preferred stock
The potential common shares outstanding that were excluded from the computation of diluted net loss per share attributable to common stockholders
Total	0	0	25,171
Stock options 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	8,196	8,174	6,256
Convertible notes
The potential common shares outstanding that were excluded from the computation of diluted net loss per share attributable to common stockholders
Total	0	0	2,328
Unvested 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	381	248	0
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	308	331	143
Convertible preferred stock warrants
The potential common shares outstanding that were excluded from the computation of diluted net loss per share attributable to common stockholders
Total	0	0	215

Segment and Geographic Information (Net Revenues) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 67,056	$ 62,046	$ 58,167	$ 45,577	$ 57,568	$ 60,813	$ 55,697	$ 42,600	$ 232,846	$ 216,678	$ 149,523
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									192,881	189,711	128,692
International
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									$ 39,965	$ 26,967	$ 20,831

Segment and Geographic Information (Long-Lived Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Long-lived assets by geographic region
Total	$ 24,853	$ 25,541	$ 18,411
United States
Long-lived assets by geographic region
Total	16,262	17,136	11,199
China
Long-lived assets by geographic region
Total	7,130	6,642	5,974
Other
Long-lived assets by geographic region
Total	$ 1,461	$ 1,763	$ 1,238

Related Party Transactions (Narrative) (Details) - KPCB Holdings, Inc. - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Related Party Transaction [Line Items]
Percentage of Company owned by related party	11.00%
Revenue from related parties	$ 2.7	$ 16.8	$ 6.4

Quarterly Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Information Disclosure [Abstract]
Net revenues	$ 67,056	$ 62,046	$ 58,167	$ 45,577	$ 57,568	$ 60,813	$ 55,697	$ 42,600	$ 232,846	$ 216,678	$ 149,523
Cost of revenues	45,560	44,611	41,883	33,376	41,512	44,489	42,096	33,293	165,430	161,390	120,454
Gross profit	21,496	17,435	16,284	12,201	16,056	16,324	13,601	9,307	67,416	55,288	29,069
Operating expenses:
Research and development	8,721	8,293	8,484	9,026	8,533	10,571	8,655	7,842	34,524	35,601	25,099
Sales and marketing	8,315	8,550	7,365	6,850	7,525	7,039	6,360	5,049	31,080	25,973	17,454
General and administrative	6,071	5,937	5,926	6,036	6,177	6,911	6,091	5,696	23,970	24,875	15,228
Total operating expenses	23,107	22,780	21,775	21,912	22,235	24,521	21,106	18,587	89,574	86,449	57,781
Loss from operations	(1,611)	(5,345)	(5,491)	(9,711)	(6,179)	(8,197)	(7,505)	(9,280)	(22,158)	(31,161)	(28,712)
Other expense, net	(783)	(815)	(781)	(513)	(1,258)	(580)	(3,729)	(839)	(2,892)	(6,406)	(3,578)
Loss before income taxes	(2,394)	(6,160)	(6,272)	(10,224)	(7,437)	(8,777)	(11,234)	(10,119)	(25,050)	(37,567)	(32,290)
Provision for income taxes	(416)	(141)	(124)	(182)	(305)	(130)	(151)	(65)	(863)	(651)	0
Net loss attributable to common stockholders	$ (2,810)	$ (6,301)	$ (6,396)	$ (10,406)	$ (7,742)	$ (8,907)	$ (11,385)	$ (10,184)	$ (25,913)	$ (38,218)	$ (32,290)
Net loss per share attributable to common stockholders, basic and diluted (usd per share)	$ (0.07)	$ (0.15)	$ (0.15)	$ (0.25)	$ (0.19)	$ (0.22)	$ (0.29)	$ (5.97)	$ (0.62)	$ (1.24)	$ (25.73)