Itron Networked Solutions (SSNI) 10-K 2 Mar 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Feb. 20, 2015	Jun. 30, 2014
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	FALSE
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Trading Symbol	ssni
Entity Registrant Name	SILVER SPRING NETWORKS INC
Entity Central Index Key	1180079
Current Fiscal Year End Date	-19
Entity Filer Category	Accelerated Filer
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Public Float			$471
Entity Common Stock, Shares Outstanding		49,392,472

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets:
Cash and cash equivalents	$60,457	$82,596
Short-term investments	60,339	63,256
Accounts receivable	54,740	69,724
Inventory	6,722	4,350
Deferred cost of revenue	29,585	37,460
Deferred tax assets	5,278	350
Prepaid expenses and other current assets	5,146	4,408
Total current assets	222,267	262,144
Property and equipment, net	12,860	12,364
Goodwill and intangible assets	8,221	671
Deferred cost of revenue, non-current	303,445	238,663
Deferred tax assets, non-current	354	1,613
Other long-term assets	1,047	896
Total assets	548,194	516,351
Current liabilities:
Accounts payable	27,530	31,317
Accrued liabilities	23,258	21,282
Deferred revenue	91,688	111,293
Current portion of capital lease obligations	1,163	1,615
Deferred tax liability	249	1,176
Total current liabilities	143,888	166,683
Deferred revenue, non-current	517,905	413,360
Deferred tax liability, non-current	5,146	187
Other liabilities	15,074	14,239
Total liabilities	682,013	594,469
Commitments and contingencies (Note 6)
Stockholders' deficit:
Common stock, $0.001 par value; 1,000,000 shares authorized; 49,062 and 47,384 shares issued and outstanding as of December 31, 2014 and 2013, respectively	47	46
Additional paid-in capital	573,344	538,967
Accumulated other comprehensive income (loss)	-779	130
Accumulated deficit	-706,431	-617,261
Total stockholders' deficit	-133,819	-78,118
Total liabilities and stockholders deficit	$548,194	$516,351

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Consolidated Balance Sheets [Abstract]
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	49,062,000	47,384,000
Common stock, shares outstanding	49,062,000	47,384,000

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue:
Product revenue	$129,333	$224,310	$162,623
Service revenue	61,955	102,548	34,114
Total revenue, net	191,288	326,858	196,737
Cost of revenue:
Product cost of revenue	77,158	150,315	115,325
Service cost of revenue	57,793	61,189	49,693
Total cost of revenue	134,951	211,504	165,018
Gross profit	56,337	115,354	31,719
Operating expenses:
Research and development	64,771	77,018	61,998
Sales and marketing	36,388	34,931	29,104
General and administrative	41,260	45,160	29,261
Restructuring	1,789
Total operating expenses	144,208	157,109	120,363
Operating loss	-87,871	-41,755	-88,644
Other income (expense), net:
Interest income	316	86	4
Interest expense	-132	-1,199	-4,296
Other expense, net	-61	-39	-269
Conversion of promissory notes and remeasurement of warrants and derivatives		-23,676	3,878
Other income (expense), net	123	-24,828	-683
Loss before income taxes	-87,748	-66,583	-89,327
Provision for income taxes	1,422	224	390
Net loss	-89,170	-66,807	-89,717
Deemed dividend to convertible preferred stockholders		-105,000
Net loss attributable to common stockholders	($89,170)	($171,807)	($89,717)
Net loss per share
Basic and diluted	($1.84)	($4.54)	($24.45)
Weighted average shares used to compute net loss per share
Basic and diluted	48,377	37,877	3,670

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Loss (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Consolidated Statements of Comprehensive Loss [Abstract]
Net loss	($89,170)	($66,807)	($89,717)
Other comprehensive income (loss):
Change in foreign currency adjustment	-770	182	-119
Net unrealized holding gain (loss) on available for sale investments (net of tax effect of $0, $51, and $0)	-139	84
Other comprehensive income (loss)	-909	266	-119
Comprehensive loss	($90,079)	($66,541)	($89,836)

Consolidated_Statements_of_Com1

Consolidated Statements of Comprehensive Loss (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Consolidated Statements of Comprehensive Loss [Abstract]
Net unrealized holding gain (loss) on available for sale investments, tax effect	$0	$51,000	$0

Consolidated_Statements_Of_Con

Consolidated Statements Of Convertible Preferred Stock And Stockholders' Deficit (USD $)	Convertible Preferred Stock [Member]	Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated deficit [Member]	Series E convertible preferred stock [Member]	Total
In Thousands, except Share data, unless otherwise specified	Series E convertible preferred stock [Member]			Series E convertible preferred stock [Member]
Beginning Balance at Dec. 31, 2011		$270,725	$4		$35,392	($17)	($460,737)		($425,358)
Beginning Balance (in shares) at Dec. 31, 2011		22,366,000	3,600,000
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of stock options and vesting of restricted stock					831				831
Issuance of common stock upon exercise of stock options and vesting of restricted stock (in shares)			179,000
Repurchases and forfeitures of common and restricted stock					-237				-237
Repurchases and forfeitures of common and restricted stock (in shares)			-15,000
Stock-based compensation					15,092				15,092
Other comprehensive income (loss)						-119			-119
Net loss							-89,717		-89,717
Ending Balance at Dec. 31, 2012		270,725	4		51,078	-136	-550,454		-499,508
Ending Balance (in shares) at Dec. 31, 2012		22,366,000	3,764,000
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of stock options and vesting of restricted stock			1		2,926				2,926
Issuance of common stock upon exercise of stock options and vesting of restricted stock (in shares)			1,644,000
Shares withheld related to net share settlement of restricted stock					-8,019				-8,019
Shares withheld related to net share settlement of restricted stock (in shares)			-422,000
Discount on series E preferred stock	-105,000			105,000				105,000
Deemed dividend to Series E preferred stock	105,000			-105,000				-105,000
Conversion of preferred stock to common stock		-270,725	32		270,693				270,725
Conversion of preferred stock to common stock (in shares)		-22,366,000	32,407,000
Conversion of preferred stock warrants to common stock warrants					66				66
Conversion of convertible promissory notes			3		79,437				79,441
Conversion of convertible promissory notes (in shares)			3,765,000						32,406,995
Issuance of common stock from private placement			1		11,999				12,000
Issuance of common stock from private placement (in shares)			706,000
Issuance of common stock from initial public offering, net of offering costs			5		79,916				79,921
Issuance of common stock from initial public offering, net of offering costs (in shares)			5,463,000
Issuance of common stock upon net exercise of common stock warrants (in shares)			57,000
Stock-based compensation					50,871				50,871
Other comprehensive income (loss)						266			266
Net loss							-66,807		-66,807
Ending Balance at Dec. 31, 2013			46		538,967	130	-617,261		-78,118
Ending Balance (in shares) at Dec. 31, 2013			47,384,000						47,384,000
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of stock options and vesting of restricted stock			1		1,112				1,113
Issuance of common stock upon exercise of stock options and vesting of restricted stock (in shares)			1,658,000
Shares withheld related to net share settlement of restricted stock			-1		-6,452				-6,453
Shares withheld related to net share settlement of restricted stock (in shares)			-473,000
Issuance of common stock in connection with employee stock purchase plan			1		5,906				5,907
Issuance of common stock in connection with employee stock purchase plan (in shares)			493,000
Stock-based compensation					33,811				33,811
Other comprehensive income (loss)						-909			-909
Net loss							-89,170		-89,170
Ending Balance at Dec. 31, 2014			$47		$573,344	($779)	($706,431)		($133,819)
Ending Balance (in shares) at Dec. 31, 2014			49,062,000						49,062,000

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows used in operating activities:
Net loss	($89,170,000)	($66,807,000)	($89,717,000)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Deferred taxes	-225,000	-205,000	-298,000
Depreciation and amortization	6,467,000	6,646,000	7,255,000
Stock-based compensation	33,861,000	52,504,000	15,092,000
Conversion of promissory notes and remeasurement of warrants and derivatives		23,676,000	-3,878,000
Non-cash interest expense on convertible notes		935,000	1,461,000
Other non-cash adjustments	431,000	333,000	178,000
Changes in operating assets and liabilities:
Accounts receivable	15,554,000	-13,245,000	-23,177,000
Inventory	-2,271,000	3,381,000	-5,246,000
Prepaid expenses and other current assets	-724,000	-1,153,000	1,109,000
Deferred cost of revenue	-56,907,000	-30,960,000	-38,860,000
Other long-term assets	918,000	4,504,000	-3,446,000
Accounts payable	-4,120,000	2,848,000	10,883,000
Accrued liabilities	998,000	4,820,000	-3,398,000
Customer deposits	321,000	-61,000	-7,046,000
Deferred revenue	84,590,000	16,597,000	107,596,000
Other liabilities	1,512,000	-3,799,000	7,214,000
Net cash (used in) provided by operating activities	-8,765,000	14,000	-24,278,000
Cash flows used in investing activities:
Changes in restricted cash			140,000
Payments for business acquisitions, net of cash and cash equivalents acquired	-8,726,000
Proceeds from sales of available-for-sale investments	53,450,000	9,122,000
Proceeds from maturities of available-for-sale investments	6,750,000
Purchases of available-for-sale investments	-57,671,000	-72,339,000
Purchases of property and equipment	-6,073,000	-3,950,000	-4,854,000
Net cash used in investing activities	-12,270,000	-67,167,000	-4,714,000
Cash flows provided by (used in) financing activities:
Payment upon termination of preferred stock warrants of a related party		-12,000,000
Proceeds from initial public offering, net of offering costs		84,247,000
Proceeds from private placement of common stock with a related party		12,000,000
Payments on capital lease obligations	-1,550,000	-2,034,000	-1,312,000
Proceeds from sale-leaseback of property and equipment			1,676,000
Proceeds from issuance of convertible promissory note			28,993,000
Proceeds from issuance of common stock, net of repurchases	7,020,000	2,909,000	594,000
Taxes paid related to net share settlement of equity awards	-6,453,000	-8,019,000
Net cash (used in) provided by financing activities	-983,000	77,103,000	29,951,000
Effect of exchange rate changes on cash	-121,000
Net (decrease) increase in cash and cash equivalents	-22,139,000	9,950,000	959,000
Cash and cash equivalents-beginning of period	82,596,000	72,646,000	71,687,000
Cash and cash equivalents-end of period	60,457,000	82,596,000	72,646,000
Supplemental cash flow information-cash paid for income taxes	659,000	233,000	801,000
Supplemental cash flow information-cash paid for interest	132,000	263,000	427,000
Non-cash investing and financing activities:
Conversion of convertible preferred stock into common stock		270,725,000
Fair value of common stock issued on conversion of convertible promissory notes		79,441,000
Deferred offering costs not yet paid		20,000
Property and equipment acquired under capital lease		1,767,000	2,915,000
Leasehold improvements funded by lease incentives	$650,000

Description_of_Business_and_Su

Description of Business and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
Description of Business and Summary of Significant Accounting Policies [Abstract]
Description of Business and Summary of Significant Accounting Policies	1. DESCRIPTION OF BUSINESS, BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES
	DESCRIPTION OF BUSINESS
	Silver Spring Networks, Inc. (the “Company”, “we”, “us” and “our”) has over ten years of experience creating, building and successfully deploying large scale networks and solutions enabling the “internet of things” for critical infrastructure. The “internet of things” refers to a system where a diversity of physical devices have the capacity to communicate using internet technologies. Our first area of focus was in energy, creating a leading grid network by applying advanced networking technology and solutions to the power grid. We have recently broadened beyond the smart grid to networking other critical infrastructure such as street lights, enabling smarter and more efficient cities.
	BASIS OF PRESENTATION
	The consolidated financial statements and accompanying notes have been prepared in accordance with accounting principles generally accepted in the United States, or GAAP. The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. Intercompany balances and transactions have been eliminated in consolidation.
	SIGNIFICANT ACCOUNTING POLICIES
	Use of Estimates
	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and the accompanying notes during the reporting period. Estimates are used for revenue and cost recognition, inventory valuation, warranty obligations, stock-based compensation, valuation of assets acquired and liabilities assumed in a business combination, classification of current and non-current deferred revenue and deferred cost of revenue, income taxes and deferred income tax assets and associated valuation allowances. These estimates generally involve complex issues and require judgments, involve the analysis of historical and prediction of future trends, can require extended periods of time to resolve and are subject to change from period to period. Actual results may differ materially from management’s estimates.
	Cash, Cash Equivalents and Short-term Investments
	Cash equivalents consist of highly liquid investments with insignificant interest rate risk and original maturities at the time of purchase of three months or less, and consist of money market funds. Short-term investments consist of high grade investment securities with original maturities at the time of purchase of greater than three months, and are available for use in current operations. We classify all of our cash equivalents and short-term investments as available-for-sale, which are recorded at fair value. Unrealized gains and losses are included in accumulated other comprehensive income (loss) in stockholders’ deficit. Realized gains and losses are included in other income and expense, net. We evaluate our short-term investments for impairment each reporting period. Determining whether a decline in fair value is other-than-temporary requires management judgment based on the specific facts and circumstances of each security. We consider various factors in determining whether to recognize an impairment charge, including the length of time the investment has been in a loss position, the extent to which the fair value has been less than the our cost basis, the investment's financial condition, and near-term prospects of the investee. If we determine that the decline in an investment's fair value is other than temporary, the difference is recognized as an impairment loss in its consolidated statements of operations. Amounts are reclassified out of accumulated other comprehensive income (loss) into earnings using the specific identification method.
	Inventory
	Inventory is stated at the lower of cost or market. Cost is computed using standard cost, which approximates actual cost on a first-in, first-out basis. The determination of market value involves numerous judgments including estimated average selling prices based upon recent sales volumes, industry trends, existing customer orders and current contract prices. We evaluate our ending inventories for excess quantities and obsolescence based on forecasted demand within specific time horizons, technological obsolescence, and an assessment of any inventory that is not of saleable condition. Forecasted demand requires management estimates and is subject to several uncertainties including market and economic conditions, technology changes and new product introductions. Actual demand may differ from forecasted demand, and such differences may have a material effect on recorded inventory values and operating results.
	In addition, we enter into purchase commitments with third-party contract manufacturers to manage lead times and meet product forecasts and with other parties to purchase various key components used in the manufacture of our products. Accruals are established for estimated losses on purchased components for which we believe it is probable that they will not be recoverable in future operations. To the extent that such forecasts are not achieved, commitments and associated accruals may change.
	Revenue Recognition
	We generally market our products and services for our advanced metering, distribution automation and demand-side management solutions directly to customers. For our advanced metering solution, we contract with third-party device manufacturers, which integrate our communications modules into their meters. Our advanced metering solution, which includes our UtilOS network operating system, UtilityIQ software suite, networking hardware, and communications modules, provides utilities with two-way communication from our communications modules to the utility’s back office. Our hardware devices include UtilOS embedded software, which functions together with the tangible hardware elements to deliver the tangible products’ essential functionality. Our UtilityIQ software suite of products includes software that is not embedded with the tangible hardware elements, but that is also necessary to deliver the tangible products’ essential network functionality, as well as other application software that provides additional functionality to the network solution. We derive revenue from sales of products, including hardware and software, as well as services, including network design and deployment support, managed services and SaaS, and ongoing customer support. We enter into separate arrangements with third-party device manufacturers to integrate our communications modules with their meters pursuant to our customers’ specifications. While we may receive payment directly from these third-party device manufacturers, the timing of revenue recognition related to communications modules delivered to third-party device manufacturers is ultimately determined based upon acceptance by our customers. Substantially all of our sales of communications modules have been fulfilled through third-party device manufacturers in this manner.
	We enter into multiple deliverable arrangements with customers to deploy our networking platform and solutions, which include the delivery of hardware and software, as well as services.
	Judgment is required in determining the separate units of accounting, which depends on whether the delivered items have standalone value to customers. When we sell our products and services separately, or when the customer could resell them on a standalone basis, we treat the delivered elements as having standalone value. In our typical customer arrangements, we consider the following to be separate units of accounting: (i) our hardware together with the related embedded software; (ii) our network management software within our UtilityIQ suite that provides the tangible product’s essential network functionality and related hardware for which the network management software is intended to be used; (iii) other application software within our UtilityIQ suite not essential for the customer to obtain functionality of the hardware; and (iv) our service offerings, which include professional services, managed services and SaaS, and ongoing customer support. We determine total arrangement consideration, and exclude amounts that are contingent upon the delivery of additional items or meeting other specified performance conditions, including potential refunds or penalty provisions. We allocate the total arrangement consideration to the deliverables based on our determination of the units of accounting and their relative selling prices. As we have not yet established vendor-specific objective evidence, or VSOE, or identified third-party evidence of fair value for these units of accounting, we use our best estimate of selling price to perform the relative fair value allocation. Judgment is also required in determining how to measure and allocate arrangement consideration among the separate units of accounting. The process for performing an assessment of our best estimate of selling price for our products and services is based on quantitative and qualitative aspects of multiple factors. These factors include market conditions, such as competitive alternatives and pricing practices, as well as company-specific factors, such as standalone sales, nature and size of the customer, contractually stated prices, costs to manufacture products or provide services and profit objectives. In establishing such profit objectives, we consider prices in previous contracts, size of the transaction, and the drivers, if any, that could influence future margins.
	The following revenue recognition criteria are applied to the units of accounting in all utility customer arrangements, as well as those in which orders of communications modules are fulfilled through third party device manufacturers as described above. We do not recognize revenue for a unit of accounting until all of the following criteria have been met:
		·		Persuasive evidence of an arrangement exists. Binding contracts or purchase orders are used to determine the existence of an arrangement.
		·		Delivery has occurred. Shipping documents and customer acceptance provisions, where applicable, are used to verify delivery.
		·		The fee is fixed or determinable. We assess whether the fee is fixed or determinable based on the payment terms associated with the transaction and whether the sales price is subject to refund or adjustment.
		·		Collectibility is reasonably assured. We assess collectibility based primarily on creditworthiness of the customer or third party device manufacturer as determined by credit assessments and payment history.
	Substantially all of our customer arrangements include acceptance provisions that require testing of the network against specific performance criteria. We consider the following factors in our assessment of whether the acceptance provisions are substantive:
		·		whether the criteria are based on our standard performance criteria or are customer-specific;
		·		if the criteria are customer-specific, availability of objective and sufficient evidence to  reliably demonstrate that the delivered products and services will meet all of the specified criteria prior to receipt of customer acceptance;
		·		our experience with similar types of arrangements or products, as well as our experience with the specific customer;
		·		whether we would be successful in enforcing a claim for payment even in the absence of acceptance confirmation from the customer;
		·		the nature and complexity of the acceptance testing, including the planned duration of the acceptance period; and
		·		the significance of financial penalties, if any, associated with not meeting performance criteria.
	Considering our limited historical experience, we have concluded for our current arrangements with acceptance terms, revenue is not recognized until we have determined acceptance is achieved. Once we have achieved acceptance, we recognize revenue as follows:
		·		Revenue from software that functions together with the tangible hardware elements to deliver the tangible products’ essential functionality is recognized upon delivery of both the software and related hardware elements, assuming all other revenue recognition criteria are met.
		·		Application software and related post contract support services which are not considered essential to the functionality of hardware devices are within the scope of ASC 985-605.  In accordance with ASC 985-605, revenues are recognized ratably over the longest service period for post-contract customer support, or PCS, and professional services as we have not established VSOE for software or the related software elements.
		·		Revenue from our service offerings, including professional services such as network design and deployment support, managed services and SaaS, and ongoing customer support is recognized as services are delivered or on a proportional performance basis depending on the underlying pattern of performance.
		·		Revenue from hardware is recognized when title transfers.
	Amounts that are invoiced prior to a transaction meeting all of the above revenue recognition criteria, including customer acceptance criteria, are recorded in deferred revenue until such criteria are satisfied. For all periods presented herein, the amount and timing of revenue and product cost recognition has been, and for the near-term will be, dependent primarily on our ability to meet substantive customer acceptance criteria. We consider a variety of factors in estimating the timing of customer acceptance, which includes contractual milestones, project schedules, availability of resources, the nature and extent of remaining testing cycles, and other relevant information provided by our project management team. Accordingly, we expect that the timing of recognition of revenue and related product costs on both a quarterly and annual basis will not be easily predictable. In addition, it is possible that the amount of current deferred revenue and related deferred cost of revenue reflected as of a balance sheet date will be significantly higher or lower than the amount of deferred revenue and related deferred cost of revenue that is ultimately recognized as revenue and cost of revenue within the 12 months following the balance sheet date. We classify deferred revenue and deferred cost of revenue that we expect to recognize during the 12 months following the balance sheet date as current deferred revenue and current deferred cost of revenue on our balance sheet and the remainder as non-current deferred revenue and non-current deferred cost of revenue.
	Certain of our customer and third-party device manufacturer contracts include contingency provisions, which impact our revenue recognition as such contingent amounts limit the amount of the total arrangement consideration under multiple deliverable contracts that can be allocated to delivered and accepted products and services. Amounts that are invoiced prior to a transaction meeting all of the revenue recognition criteria, including contingency provisions, are recorded in deferred revenue until such provisions have lapsed. For the years ended December 31, 2014 and 2013, such amounts were $26.2 million and $45.8 million, respectively, related to those customers whose revenue which we have started recognizing. These contingencies are related to potential penalties for late delivery, liquidated damages related to failure to meet milestones or deliver specified products or services, or credits to be issued upon the failure to meet service level arrangements. The amounts that could be paid under these provisions are typically limited and capped at amounts that do not exceed the maximum contract value. Accordingly, even in situations where we have received customer acceptance, we limit the revenue recognized for accepted products and services by the amount that could be paid under these provisions. We do not recognize these deferred amounts until the provisions have lapsed.  Predicting when such provisions will lapse is subject to significant uncertainty as the timing is dependent on a variety of factors, including the progress and completion of deployments. Related to the contingency provisions described above, $4.6 million and $13.8 million, respectively, were recorded as current deferred revenue and $21.6 million and $31.9 million, respectively, were recorded as non-current revenue as of December 31, 2014 and 2013.
	In cases where we sell third-party products and services such as meters, hardware, services, software or software maintenance as part of the overall solution, we evaluate whether we act as principal or agent under the arrangement. The evaluation considers multiple factors, including whether we are the primary obligor under the arrangement with the customer, whether we bear the risk of loss and credit risk associated with the supply of third-party products and services, whether we have the ability to change the product or perform part of the service, and whether we have the ability to control the price charged to our customers for the third-party products and services. Revenue is presented on a gross basis when we conclude that we are the principal under the arrangement with respect to third-party products and services, and revenue is presented on a net basis when we conclude that we are acting as the agent. Substantially all of our revenue related to third-party products and services is recognized on a gross basis as we are generally acting as the principal under our arrangements.
	Shipping charges billed to customers were not significant for the years ended December 31, 2014, 2013, and 2012. Shipping charges are included in revenue, and the related shipping costs are included in cost of revenue in the accompanying consolidated statements of operations.
	Cost of Revenue
	Cost of revenue consists of cost of product and service revenue. Cost of product revenue includes contract manufacturing costs, including raw materials, components and associated freight, and normal yield loss. In addition, cost of product revenue includes compensation, benefits and stock-based compensation provided to our manufacturing personnel, overhead and other direct costs. Product costs are deferred upon shipment and are recognized in the period in which we recognize the related revenue. Period costs, which consist primarily of logistics costs, manufacturing ramp-up costs, expenses for inventory obsolescence, standard warranty costs and lower of cost or market adjustments are recognized in the period in which they are incurred.
	Costs of providing services include personnel-related costs, depreciation and amortization, and software hosting costs. Costs of providing services are not deferred and are included in cost of revenue in the period in which they are incurred.
	Deferred Revenue and Deferred Cost of Revenue
	Deferred revenue results from transactions where we have billed the customer for product shipped or services performed but all revenue recognition criteria have not yet been met.
	Deferred cost of revenue is recorded for products for which ownership (typically title and risk of loss) has transferred to the customer, but for which criteria for revenue recognition have not been met. We only defer tangible direct costs associated with hardware products delivered. Cost of revenue for providing services is not deferred, but is expensed in the period incurred. Deferred cost of revenue associated with deferred product revenue is recorded at the standard inventory cost at the time of shipment. We evaluate deferred cost of revenue for recoverability based on multiple factors, including whether net revenues less related direct costs will exceed the amount of deferred cost of revenue based on the terms of the overall arrangement. To the extent that deferred cost of revenue is determined to be unrecoverable, we adjust deferred cost of revenue with a charge to product cost of revenue in the current period. In connection with our recoverability assessments, we have not incurred significant impairment charges through December 31, 2014.
	We recognize deferred revenue and associated deferred cost of revenue in the consolidated statements of operations once all revenue recognition criteria have been met.
	Product Warranty
	We provide warranties for substantially all of our products. Our standard warranty period extends from one to five years. We accrue for costs of standard warranty at the time of product shipment, and record changes in estimates to warranty accruals when it is probable a liability has been incurred and the amount of loss can be reasonably estimated.
	At the time of product shipment, we estimate and accrue for the amount of standard warranty cost and record the amount as a cost of revenue. Determining the amount of warranty costs requires management to make estimates and judgments based on historical claims experience, industry benchmarks, test data and various other assumptions including estimated field failure rates that are believed to be reasonable under the circumstances. The amount of warranty costs accrued are net of warranty obligations to be fulfilled by our suppliers. The results of these judgments formed the basis for our estimate of the total charge to cover anticipated customer warranty, repair, return and replacement and other associated costs. Should actual product failure rates, claim levels, material usage or supplier warranties on parts used in our products differ from our original estimates, revisions to the estimated warranty liability could result in adjustments to our cost of revenue in future periods.
	Certain of our standard product warranty obligations require us to reimburse a customer for installation and other related costs in the event that field reliability rates fall below contractually specified thresholds. We consider the probability that we will have to pay such incremental warranty costs based on the expected performance of a delivered product when we record new warranty obligations issued in a period as well as when we determine if any changes are required to our original estimates for pre-existing warranty obligations.
	Our warranty obligations are affected by product failure rates, claims levels, material usage and supplier warranties on parts included in our products. Because our products are relatively new and we do not have the benefit of long-term experience observing products’ performance in the field, it is possible that the estimates of a product’s lifespan and incidence of claims could vary from period to period.
	In certain customer arrangements, we have provided extended warranties for periods of up to 15 years following the initial standard warranty period. We recognize revenue associated with extended warranties over the extended warranty period when the extended warranty period commences. Costs associated with providing extended warranties are expensed as incurred during the extended warranty period.
	Supplier Concentrations and Other Inventory Risks
	We have arrangements under which substantially all of our manufacturing activity is subcontracted to third-party vendors. Currently we have our manufacturing relationships with Plexus Corp. and Celestica, Inc., who provides us with a wide range of operational and manufacturing services, including material procurement, final assembly, test quality control, warranty repair, and shipment to our customers and third-party vendors. Contract manufacturing activities are conducted in the United States and are undertaken based on management’s product demand forecasts. Our contract manufacturers procure components necessary to assemble the products anticipated by management’s forecast and test the products according to our quality specifications. If the components are unused for specified periods of time, we may incur carrying charges or obsolete material charges for components that our contract manufacturers purchased to build products to meet our product demand forecasts. Our communications modules and other hardware products consist of commodity parts and certain custom components. Our components are generally available from multiple sources or suppliers. However, some components used in our products are purchased from single or limited sources.
	Finished goods are reported as inventory until title transfers to the customer. Consigned finished goods inventory that is maintained at customer locations is also reported as inventory until consumption or acceptance of the product by the customer. We account for consigned inventory on a first-in, first-out basis and record lower of cost or market or obsolete material charges when appropriate.
	Concentration of Credit and Customer Risks
	Our sales are currently concentrated with a small group of customers and third party device manufacturers principally located in the United States and Australia. In evaluating customer concentration risk, we attribute revenue to our customers, including amounts billed to third party device manufacturers for our communications modules.
	The following table summarizes the percentage of revenue related to our customers’ deployments in excess of 10% of total revenue:
		Year Ended December 31,
		2014			2013		2012
	CHED	21	%		—	%	—	%
	Progress	13			—		—
	PG&E	—			39		30
	FPL	—			20		31
	OG&E	—			—		18
Each of these total revenue percentages includes amounts related to the customers’ deployments that were billed directly to our third party device manufacturers, as well as direct revenue from the customers. We typically extend credit to our customers and third party device manufacturers and do not require collateral or other security in support of accounts receivable. We attempt to mitigate the credit risk in our trade receivables through our credit evaluation process and payment terms. We analyze the need to reserve for potential credit losses and record allowances for doubtful accounts when necessary. To date, we have not had any significant write-offs of uncollectible accounts receivable, and there was no allowance for doubtful accounts as of December 31, 2014 and 2013.
The following table summarizes the percentage of accounts receivable from customers and third party device manufacturers in excess of 10% of accounts receivable:
	December 31,
	2014			2013
Commonwealth Edison Company	19	%		10	%
Virginia Electric and Power Company	13			10
CPS	11			—
Landis + Gyr AG	—			11
Baltimore Gas and Electric Company	—			26
Advertising Costs
We expense advertising costs as incurred. Advertising costs were $2.2 million, $2.2 million, and $2.5 million for each of the years ended December 31, 2014, 2013, and 2012.
Property and Equipment, Net
Property and equipment are stated at cost less accumulated depreciation. Depreciation is calculated using the straight-line method over the following estimated useful lives:
Software	3 to 7 years
Computer and network equipment	2 to 5 years
Machinery and equipment	3 years
Furniture and fixtures	3 to 7 years
Leasehold improvements	Lesser of the lease term or the estimated useful lives of the improvements, generally 1 to 10 years
Intangible and Long-Lived Assets
We evaluate long-lived assets and amortizable intangible assets for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable in accordance with Financial Accounting Standards Board, or FASB, Accounting Standards Codification, or ASC, Topic 360, Property, Plant and Equipment. 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 (i.e., if the sum of its estimated future undiscounted cash flows used to test for recoverability is less than its carrying value), the impairment loss to be recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets. Intangible assets with definite lives are being amortized over the estimated useful lives of the related assets. Each period, we evaluate the estimated remaining useful life of purchased intangible assets and whether events or changes in circumstances warrant a revision to the remaining period of amortization. For the years ended December 31, 2014, 2013, and 2012, no impairment losses were recorded.
Goodwill
Goodwill represents the excess of the purchase price over the fair value of the net tangible and identifiable intangible assets acquired in a business combination. Goodwill is not subject to amortization but is subject to annual assessment, at a minimum, for impairment in accordance with ASC Topic 350, Intangibles — Goodwill and Other. We evaluate goodwill, at a minimum, on an annual basis and whenever events and changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Impairment of goodwill is tested at the reporting unit level. We first assesses qualitative factors to determine whether the existence of events or circumstances leads to a determination that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If, after assessing the totality of events or circumstances, it is determined it is more likely than not that the fair value of a reporting unit is less than its carrying amount, then we perform the two-step impairment test to measure the amount of the impairment loss, if any. For the years ended December 31, 2014, 2013, and 2012, no impairment losses were recorded.
Research and Development
Research and development costs are expensed as incurred. Under our current practice of developing new products, technological feasibility of the underlying software is not established until substantially all product development and testing is complete, which generally includes the development of a working model. Our products are released within a short period of time after achieving technological feasibility.
Corporate Bonus Incentive Plan
Our corporate bonus incentive plan is funded by a combination of cash and restricted stock units, at management’s discretion. We accrue and record the related corporate bonus amounts payable, both in cash and restricted stock units, under this plan in the period in which it is earned. The Compensation Committee may make incentive awards based on such terms, conditions and criteria as it considers appropriate. Stock awards issued in connection with this plan are generally fully vested at the time of grant. Because the award of share-based payments described above represents an obligation to issue a variable number of the Company’s shares determined on the basis of a monetary value derived solely on variations in an operating performance measure (and not on the basis of variations in the fair value of the entity’s equity shares), the award is considered a share-based liability in accordance with ASC Topic 480, Distinguishing Liabilities from Equity (“ASC 480”) and is remeasured to fair value each reporting period.
Stock-Based Compensation
We measure and recognize compensation expense for all stock-based awards made to employees and directors, including stock options, restricted stock, restricted stock units, and employee stock purchase plan, based on estimated fair values. The fair values of stock options and our 2012 Employee Stock Purchase Plan (please refer to Note 9. Stock Based Compensation for further discussion) are estimated at the date of grant using the Black-Scholes-Merton option pricing model, which includes assumptions for the dividend yield, expected volatility, risk-free interest rate, and expected life. The fair values of restricted stock and restricted stock units are determined based upon the fair value of the underlying common stock at the date of grant. We expense stock-based compensation, adjusted for estimated forfeitures, using the straight-line method over the vesting term of the award. Our excess tax benefits cannot be credited to stockholders’ equity until the deduction reduces cash taxes payable; accordingly, we realized $0.1 million in excess tax benefits during fiscal 2014 and no excess tax during fiscal 2013. The amount of capitalized stock-based employee compensation cost as of December 31, 2014 and 2013 was not material.
Income Taxes
We account for income taxes in accordance with ASC Topic 740, Income Taxes, which requires the asset and liability approach for financial accounting and reporting of income taxes. Deferred income taxes are recorded 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. The carrying value of net deferred tax assets reflects that we have been unable to generate sufficient taxable income in certain tax jurisdictions. We record a valuation allowance to reduce our deferred tax assets to the amount of future tax benefit that we believe is more likely than not to be realized. The deferred tax assets are still available for us to use in the future to offset taxable income, which would result in the recognition of a tax benefit and a reduction in our effective tax rate. Actual operating results and the underlying amount and category of income in future years could render our current assumptions, judgments and estimates of the realizability of deferred tax assets inaccurate, which could have a material impact on its financial position or results of operations.
We follow a two-step approach to recognizing and measuring tax benefits associated with uncertain tax positions taken or expected to be taken in a tax return. The first step is to determine if, based on the technical merits, it is more likely than not that the tax position will be sustained upon examination by a taxing authority, including resolution of any related appeals or litigation processes. The second step is to measure the tax benefit as the largest amount that is more than 50% likely to be realized upon ultimate settlement with a taxing authority. We recognize any interest and penalties related to uncertain tax positions in the provision for income taxes line of our consolidated statements of operations. Accrued interest and penalties are included within the related tax liability line in the consolidated balance sheets.
Recent Accounting Pronouncements
In May 2014, the FASB issued guidance related to revenue from contracts with customers, which supersedes the revenue recognition requirements in ASC 605, Revenue Recognition. Under this guidance, revenue is recognized when promised goods or services are transferred to customers in an amount that reflects the consideration that is expected to be received for those goods or services. The new guidance also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract.  The updated standard will replace most existing revenue recognition guidance under GAAP when it becomes effective and permits the use of either the full retrospective or cumulative effect transition method. Early adoption is not permitted. The updated standard will be effective for us in the first quarter of 2017. We have not yet selected a transition method and we are currently evaluating the effect that the updated standard will have on our consolidated financial statements and related disclosures.

Net_Loss_Per_Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2014
Net Loss Per Share [Abstract]
Net Loss Per Share	2. NET LOSS PER SHARE
	In connection with our IPO, all of our outstanding convertible preferred stock converted into common stock. In addition, we recognized a deemed dividend of $105.0 million to common stockholders on the date of conversion. Basic net loss per share applicable to common stockholders is computed by dividing the net loss applicable to common stockholders by the weighted-average number of shares of common stock outstanding during the period. Diluted net loss per share applicable to common stockholders is computed by giving effect to all potential shares of common stock, including convertible debt, stock options, warrants and convertible preferred stock, to the extent dilutive. As we have incurred losses during each of the last three fiscal years, basic and diluted net loss per share was the same for each period presented as the inclusion of all potential common shares outstanding would have been anti-dilutive.
	The following table sets forth the computation of historical basic and diluted net loss per share (in thousands, except per share data):
		Year Ended December 31,
		2014			2013		2012
	Net loss	$	-89,170		$	-66,807	$	-89,717
	Deemed dividend to convertible preferred shareholders		—			-105,000		—
	Net loss attributable to common stockholders	$	-89,170		$	-171,807	$	-89,717
	Weighted-average shares used to compute net loss per share, basic and diluted		48,377			37,877		3,670
	Basic and diluted net loss per share attributable to common stockholders	$	-1.84		$	-4.54	$	-24.45
	The following potential common shares outstanding were excluded from the computation of diluted net loss per share because including them would have been anti-dilutive (in thousands):
		Year Ended December 31,
		2014		2013		2012
	Employee equity incentive plans	6,922		7,760		4,847
	Warrants to purchase convertible preferred stock	—		—		386
	Warrants to purchase common stock	—		—		50
	Convertible preferred stock	—		—		22,366
	Total common stock equivalents	6,922		7,760		27,649
	Also excluded from the computation of diluted net loss per share was the impact of issuing shares for the potential conversion of the subordinated convertible notes, which converted in connection with our IPO.

Cash_Cash_Equivalents_And_Shor

Cash, Cash Equivalents, And Short-Term Investments	12 Months Ended
	Dec. 31, 2014
Cash, Cash Equivalents, And Short-Term Investments [Abstract]
Cash, Cash Equivalents, And Short-Term Investments	3. CASH, CASH EQUIVALENTS, AND SHORT-TERM INVESTMENTS
	Cash, cash equivalents, and short-term investments consisted of the following as of December 31, 2014 (in thousands):
		Amortized		Unrealized		Unrealized		Estimated
		Cost		Gains		Losses		Fair Value
	Current assets:
	Cash	$	54,239	$	—	$	—	$	54,239
	Cash equivalents:
	Money market mutual funds		6,218		—		—		6,218
	Total cash and cash equivalents		60,457		—		—		60,457
	Short-term fixed income securities:
	U.S. government and agency obligations		38,718		46		-18		38,746
	U.S. and foreign corporate debt securities		19,625		9		-33		19,601
	Foreign governments and multi-national agency obligations		2,000		—		-8		1,992
	Total short-term investments		60,343		55		-59		60,339
	Total cash, cash equivalents and short-term investments	$	120,800	$	55	$	-59	$	120,796
	Cash, cash equivalents, and short-term investments consisted of the following as of December 31, 2013 (in thousands):
		Amortized		Unrealized		Unrealized		Estimated
		Cost		Gains		Losses		Fair Value
	Current assets:
	Cash	$	52,346	$	—	$	—	$	52,346
	Cash equivalents:
	Money market mutual funds		30,250		—		—		30,250
	Total cash and cash equivalents		82,596		—		—		82,596
	Short-term fixed income securities:
	U.S. government and agency obligations		41,991		84		-21		42,054
	U.S. and foreign corporate debt securities		18,366		76		-1		18,441
	Foreign governments and multi-national agency obligations		2,764		—		-3		2,761
	Total short-term investments		63,121		160		-25		63,256
	Total cash, cash equivalents and short-term investments	$	145,717	$	160	$	-25	$	145,852
	As of December 31, 2014,  approximately 46% and 42% of our cash, cash equivalents, and short-term investments were held with two financial institutions. As of December 31, 2013, approximately 41%,  34%, and 21% of our cash, cash equivalents, and short-term investments were held with three financial institutions.
	Contractual Maturities
	The contractual maturities of cash equivalents and short-term investments held at December 31, 2014 consisted of the following (in thousands):
		31-Dec-14				31-Dec-13
		Amortized		Aggregate		Amortized		Aggregate
		Cost Basis		Fair Value		Cost Basis		Fair Value
	Due within one year	$	20,588	$	20,599	$	44,477	$	44,474
	Due after 1 year through 3 years		45,973		45,958		48,894		49,032
	Total cash equivalents and short-term investments	$	66,561	$	66,557	$	93,371	$	93,506
	The following table presents gross unrealized losses and fair values for those investments that were in an unrealized loss position as of December 31, 2014 and 2013, aggregated by investment category and the length of time that individual securities have been in a continuous loss position (in thousands):
		As of December 31, 2014				As of December 31, 2013
		Total (Less Than 12 Months)				Total (Less Than 12 Months)
		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
	U.S. and foreign corporate debt securities	$	14,563	$	-33	$	4,247	$	-1
	Foreign governments and multi-national agency obligations		1,992		-8		2,761		-3
	U.S. government and agency obligations		13,523		-18		12,566		-21
	Total	$	30,078	$	-59	$	19,574	$	-25
	As of December 31, 2014 and 2013, there were no investments with unrealized losses for a period in excess of 12 months.
	We periodically review our marketable debt securities for other-than-temporary impairment. We consider factors such as the duration, severity and the reason for the decline in value, the potential recovery period and our intent to sell. We also consider whether it is more likely than not that we will be required to (i) sell the debt securities before recovery of their amortized cost basis, and (ii) the amortized cost basis cannot be recovered as a result of credit losses. As of December 31, 2014, we anticipate that we will recover the entire amortized cost basis of such available-for-sale debt securities and has determined that no other-than-temporary impairments associated with credit losses were required to be recognized during the year ended December 31, 2014 and 2013. There were no material gross realized gains or losses from available-for-sale securities during the years ended December 31, 2014 and 2013.

Fair_Value_Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2014
Fair Value Measurements [Abstract]
Fair Value Measurements	4.  FAIR VALUE MEASUREMENTS
	We determine the fair values of our financial instruments based on a fair value hierarchy, which requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The classification of a financial asset or liability within the hierarchy is based upon the lowest level input that is significant to the fair value measurement. Under ASC Topic 820, Fair Value Measurement and Disclosures, the fair value hierarchy prioritizes the inputs into three levels that may be used to measure fair value. The fair value framework requires the categorization of assets and liabilities into three levels based upon the assumptions (inputs) used to price the assets or liabilities. The guidance for fair value measurements requires that assets and liabilities carried at fair value be classified and disclosed in one of the following categories:
	Level 1—Quoted prices (unadjusted) in active markets for identical assets or liabilities.
	Level 2—Observable inputs other than quoted prices included in Level 1, such as quoted prices for similar assets or liabilities in active markets; quoted prices for identical or similar assets or liabilities in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the asset or liability.
	Level 3—Unobservable inputs in which there is little or no market data, which requires us to develop our own assumptions.
	Level 1 measurements are obtained from real-time quotes for transactions in active exchange markets involving identical assets. Level 2 measurements are obtained from readily available pricing sources for comparable instruments, identical instruments in less active markets, or models using market observable inputs. We did not have any transfers of financial instruments between valuation levels during the year ended December 31, 2014 and 2013.
	Assets Measured at Fair Value on a Recurring Basis
	As of December 31, 2014, financial assets recorded at fair value on a recurring basis were determined using the following inputs (in thousands):
		Fair Value Measurement Using
		Quoted Prices in		Significant
		Active Markets for		Other		Significant
		Identical		Observable		Unobservable
		Instruments		Inputs		Inputs
		(Level 1)		(Level 2)		(Level 3)		Total
	Cash equivalents:
	Money-market funds	$	6,218	$	—	$	—	$	6,218
	Total cash equivalents		6,218		—		—		6,218
	Short-term investments:
	U.S. Government and agency obligations		—		38,746		—		38,746
	U.S. and foreign corporate debt securities		—		19,601		—		19,601
	Foreign governments and multi-national agency obligations		—		1,992		—		1,992
	Total short-term investments		—		60,339		—		60,339
	Total assets measured at fair value	$	6,218	$	60,339	$	—	$	66,557
	As of December 31, 2013, financial assets recorded at fair value on a recurring basis were determined using the following inputs (in thousands):
		Fair Value Measurement Using
		Quoted Prices in		Significant
		Active Markets for		Other		Significant
		Identical		Observable		Unobservable
		Instruments		Inputs		Inputs
		(Level 1)		(Level 2)		(Level 3)		Total
	Cash equivalents:
	Money-market funds	$	30,250	$	—	$	—	$	30,250
	Total cash equivalents		30,250		—		—		30,250
	Short-term investments:
	U.S. Government and agency obligations		—		42,054		—		42,054
	U.S. and foreign corporate debt securities		—		18,441		—		18,441
	Foreign governments and multi-national agency obligations		—		2,761		—		2,761
	Total short-term investments		—		63,256		—		63,256
	Total assets measured at fair value	$	30,250	$	63,256	$	—	$	93,506
	As of December 31, 2014 and 2013, there were no liabilities that are measured and recorded at fair value on a recurring basis.
	As of December 31, 2014 and 2013, there were no assets and liabilities that are measured and recorded at fair value on a nonrecurring basis.
	Assets and Liabilities Not Measured at Fair Value
	The carrying amounts of our accounts receivable, accounts payable, and other accrued liabilities approximate fair value due to their short maturities.

Business_Acquisition

Business Acquisition	12 Months Ended
	Dec. 31, 2014
Business Acquisition [Abstract]
Business Acquisition
	5.  BUSINESS ACQUISITION
	On May 6, 2014, we entered into a purchase agreement to acquire 100% of the outstanding shares of Streetlight.Vision, a company incorporated under the laws of France, which provides street light control and management software. On May 23, 2014 (the “acquisition date”), we completed the acquisition of Streetlight.Vision SAS, a société par actions simplifiée, (“SLV”) for a purchase price of $8.8 million in cash consideration, of which $2.6 million was deposited in an escrow account to satisfy indemnification claims that we may have for a period 24 months pursuant to the terms of the purchase agreement.  If there remains more than $1.3 million in the escrow account 12 months after the completion of the acquisition after taking into account any pending indemnification claims, such amount over $1.3 million shall be paid to the SLV shareholders.  The remaining $1.3 million will be paid to the SLV shareholders after the conclusion of the 24-month period, subject to any pending indemnification claims.  The total cash consideration paid was to acquire 100% of the shares of SLV on a debt-free, cash-free basis and payment of outstanding indebtedness in the aggregate amount of Euro 1.2 million (or approximately $1.6 million).
	SLV, a software and consulting company, provides central management software for street light and street applications. SLV develops a central management software that commands, controls, monitors, and configures networks of street lights, as well as various other devices connected to the street lights electrical grid through various power line or radiofrequency technologies. It provides street lights monitoring and control solutions to street lights maintenance companies, manufacturers of street lights control systems, manufacturers of street lights ballasts, manufacturers of LED and induction fixtures, and energy service providers worldwide. The acquisition of SLV will enable us to expand our footprint into the smart city market.
	In accordance with ASC Topic 805, Business Combinations (“ASC 805”), the acquisition of SLV was accounted for under the acquisition method of accounting. Under the acquisition method of accounting, the total purchase consideration, assets acquired and the liabilities assumed is measured at fair value as of the date of acquisition when control is obtained. The fair value of the consideration transferred and the assets acquired and liabilities assumed was determined by us and in doing so relied in part upon a third-party valuation report to measure the identifiable intangible assets acquired and obligations related to deferred revenue. The following table summarizes the fair value of total consideration transferred for the SLV acquisition, the total fair value of net identifiable assets acquired and the resulting goodwill recorded (in thousands):
	Cash consideration	$	8,749
	Less: Fair value of net identifiable assets acquired		-4,064
	Goodwill	$	4,685
	The following table summarizes the estimated fair value of the assets acquired and liabilities assumed at the acquisition date. The estimated fair value of the identifiable assets acquired and liabilities assumed in the acquisition is based on management’s best estimates. As we finalize certain valuation assumptions, the provisional measurements of identifiable assets, liabilities, the resulting goodwill, and deferred income taxes are subject to change, and the final purchase price accounting could be different from the amounts presented herein.
	Assets acquired and liabilities assumed as of May 23, 2014 (in thousands):
	Net tangible assets, excluding deferred revenue	$	621
	Deferred revenue		-350
	Intangible assets subject to amortization:
	Developed technology		1,600
	Customer relationships		2,100
	Trade name		300
	In-process research and development (IPR&D)		300
	Deferred tax liabilities in connection with acquired intangible
	assets and other fair value adjustments, net		-507
	Total fair value of net identifiable assets acquired	$	4,064
	Certain closing balance sheet items in connection with the acquisition of SLV were finalized during the fourth quarter of 2014. As a result, the net assets acquired decreased by $0.1 million which was accounted for as measurement period adjustments in the fourth quarter of 2014 with a corresponding adjustment to goodwill.
	Intangible assets of $4.3 million consist primarily of developed technology, customer relationships, trade name and IPR&D. Developed technology relates to SLV’s technology and knowhow which is currently generating revenue. Customer relationships relate to SLV’s ability to sell existing, in-process and future versions of its products to its existing customers. Trade names represent future value to be derived from the use of existing trade names. Developed technology, IPR&D and trade name were valued using the relief from royalty method based on discounted cash flow (“DCF”). A discount rate of 17% was used to value developed technology, 20% to value IPR&D, and 19% to value trade name. The customer relationships were valued using multi-period excess earnings method under the income approach based on DCF and using a discount rate of 19%. The discount rate used in the present value calculation was derived from a weighted average cost of capital (“WACC”) analysis, adjusted to reflect additional benefits or risks related to each asset’s characteristics. The intangible assets of $4.0 million are subject to amortization and we expect to amortize these intangible assets on a straight-line basis over their expected useful lives of approximately four to seven years. Of the total purchase consideration, $4.7 million was recognized as goodwill, which represents the excess of the purchase consideration of an acquired business over the fair value of the underlying net assets acquired and liabilities assumed. The goodwill arising from the SLV acquisition is largely attributable to the synergies expected to be realized. None of the goodwill recorded as part of the SLV acquisition will be deductible for income tax purposes.
	We recognized $0.4 million of acquisition-related costs that were expensed in the year ended December 31, 2014. These costs are included as part of general and administration costs in the consolidated statement of operations.
	The amounts of revenue and earnings of SLV included in our consolidated statement of operations from the acquisition date to the period ending December 31, 2014 are as follows (in thousands):
	Revenues	$	900
	Net loss	$	-509

Goodwill_And_Intangible_Assets

Goodwill And Intangible Assets	12 Months Ended
	Dec. 31, 2014
Goodwill And Intangible Assets [Abstract]
Goodwill And Intangible Assets	6. GOODWILL AND INTANGIBLE ASSETS
	Goodwill:
	The following table presents goodwill as of December 31, 2014 and 2013 and changes in the carrying amount of goodwill (in thousands):
			December 31,
				2014			2013
	Balance, beginning of period		$	447		$	447
	Goodwill acquired during the period			4,685			-
	Goodwill measurement period adjustment			85			-
	Currency translation adjustment			-488			-
	Balance, end of period		$	4,729		$	447
	During the year ended December 31, 2014, we recorded goodwill of $4.7 million in connection with our acquisition of SLV. In addition, we also adjusted goodwill by $0.1 million in connection with our acquisition of SLV as a measurement period adjustment during the year ended December 31, 2014. Of the total goodwill, goodwill related to SLV is designated in a currency other than United States Dollars and is adjusted each reporting period for the change in foreign exchange rates between the balance sheet dates.
	Intangible Assets:
	The following table summarizes the gross carrying amount and accumulated amortization for the intangible assets resulting from acquisitions:
	The following table summarizes the gross carrying amount and accumulated amortization for the intangible assets resulting from acquisitions:
		Developed Technology			Customer Relationships			Trade Name		In-process R&D		Total
	Amortization Period	4-5 years			2-7 years			6 years		Indefinite
	Cost:
	Balance at December 31, 2012	$	962		$	260		$	—	$	—	$	1,222
	Balance at December 31, 2013	$	962		$	260		$	—	$	—	$	1,222
	Acquired as a part of SLV acquisition		1,600			2,100			300		300		4,300
	Currency translation adjustment		-166			-220			-31		-31		-448
	Balance at December 31, 2014	$	2,396		$	2,140		$	269	$	269	$	5,074
	Accumulated Amortization:
	Balance at December 31, 2012	$	546		$	260		$	—	$	—	$	806
	Amortization expense		192			—			—		—		192
	Balance at December 31, 2013	$	738		$	260		$	—	$	—	$	998
	Amortization expense		417			169			28		—		614
	Currency translation adjustment		-16			-12			-2		—		-30
	Balance at December 31, 2014	$	1,139		$	417		$	26	$	—	$	1,582
	Intangible assets, net at December 31, 2014	$	1,257		$	1,723		$	243	$	269	$	3,492
	Intangible assets, net at December 31, 2013	$	224		$	—		$	—	$	—	$	224
	Intangible assets subject to amortization are amortized over their useful lives as shown in the table above. During the year ended December 31, 2014, we recorded intangible assets of $4.3 million in connection with our acquisition of SLV. The intangible assets acquired in connection with acquisition of SLV are designated in a currency other than United States Dollars and are adjusted each reporting period for the change in foreign exchange rates between the balance sheet dates.
	The following table illustrates the amortization expense included in the consolidated statements of operations for the years ended December 31, 2014 (in thousand):
		Year Ended
		December 31,
		2014
	Cost of revenue	$	417
	Selling and marketing		197
	Total	$	614
	The estimated future amortization expense of purchased intangible assets with definite lives for the next five years is as follows (in thousands):
			Year Ended
	2015		$	704
	2016			672
	2017			672
	2018			463
	2019			313
	2020 and thereafter			399
			$	3,223

Convertible_Preferred_Stock_An

Convertible Preferred Stock And Preferred Stock Warrants	12 Months Ended
	Dec. 31, 2014
Common Stock [Abstract]
Convertible Preferred Stock And Preferred Stock Warrants	7. CONVERTIBLE PREFERRED STOCK AND PREFERRED STOCK WARRANTS
	Convertible Preferred Stock
	In connection with our IPO in March 2013, our previously authorized and outstanding convertible preferred stock was converted into 32,406,995 shares of common stock. Included in this amount were incremental shares issued to Series D and Series E preferred stockholders in accordance with their contractual conversion rights which stated that if the IPO conversion price for Series D and Series E preferred stockholders was below $38.927 and $50.00 per share, respectively, then we would issue to the eligible holders additional shares of common stock for no additional consideration pursuant to an automatic adjustment in our certificate of incorporation. The additional shares resulted in a beneficial conversion feature for Series E preferred stock and we recognized a $105.0 million deemed dividend to Series E preferred stockholders at the conversion date. This non-cash charge impacts net loss applicable to our common stockholders and basic and diluted net loss per share applicable to common stockholders.
	Warrant Termination and Concurrent Private Placement with a Related Party
	Prior to our IPO, entities affiliated with Foundation Capital, together Foundation Capital, beneficially owned 32.7% of our common stock. Foundation Capital is considered a related party, as Warren Weiss, a general partner with Foundation Capital, is also a member of our Board of Directors. Foundation Capital held warrants to purchase 41,993 shares of our Series A Preferred Stock and 333,333 shares of our Series C Preferred Stock prior to our IPO.
	All such warrants terminated immediately prior to the effectiveness of our IPO in exchange for the aggregate payment by us of $12.0 million to these entities. In connection with the transaction, we reduced our preferred stock warrant liability by $11.2 million and recorded a loss of $0.8 million in the year ended December 31, 2013.
	We also entered into a private placement purchase agreement whereby Foundation Capital purchased an aggregate of $12.0 million of shares of our common stock at the same price as the price offered to the public, or 705,881 shares based on the IPO price of $17.00 per share. This private placement purchase was consummated on the same day that our IPO closed.

Common_Stock

Common Stock	12 Months Ended
	Dec. 31, 2014
Common Stock [Abstract]
Common Stock
	8. COMMON STOCK
	Initial Public Offering
	In March 2013, we completed our IPO in which we issued and sold 5,462,500 shares of common stock at a public offering price of $17.00 per share. We received net proceeds of $84.2 million after deducting underwriting discounts and commissions of $6.5 million and offering costs of $2.2 million incurred in fiscal 2013 prior to our IPO. In addition, we reclassified previously capitalized offering expenses of $4.2 million against the IPO proceeds in our consolidated statements of convertible preferred stock and shareholders’ deficit in the year ended December 31, 2013. Concurrently with our IPO, we issued and sold in a private placement 705,881 shares of common stock at the public offering price of $17.00 per share, which resulted in net proceeds of $12.0 million. In addition, in connection with our IPO:
		·	All of our outstanding convertible preferred stock converted into 32,406,995 shares of common stock.
		·	Our $24.0 million and $30.0 million convertible notes together with contractual accrued interest of $2.3 million converted into 3,764,954 shares of common stock. In connection with the conversion, we recorded a loss on debt extinguishments of $22.9 million.
		·	We reduced our preferred stock warrant liability by $11.2 million and recorded a loss of $0.8 million in the year ended December 31, 2013 resulting from our payment of $12.0 million as consideration for the termination of certain warrants to purchase shares of Series A preferred stock and all warrants to purchase shares of Series C preferred stock, which occurred immediately prior to the effectiveness of our IPO.
		·	We recognized stock-based compensation expense of $14.6 million in the year ended December 31, 2013 upon the effectiveness of the Registration Statement on Form S-1 in connection with our incentive bonus plans.
		·	We recognized stock-based compensation expense of approximately $4.7 million in the year ended December 31, 2013 related to the modification of stock options held by current employees.
	Restated Certificate of Incorporation and Amended and Restated Bylaws
	Our restated certificate of incorporation and amended and restated bylaws became effective upon the closing date of our IPO. Our restated certificate of incorporation: (a) eliminated the references to the terms of our existing series of preferred stock, which converted to common stock in connection with the IPO; (b) increased the authorized number of shares of common stock to 1,000,000,000 shares; (c) authorized 10,000,000 shares of undesignated preferred stock; (d) provided that holders of common stock will not be entitled to vote on amendments to the restated certificate that relate solely to the terms of any preferred stock designated by our Board of Directors if the holders of such preferred stock are entitled to vote on such amendment; (e) provided that our Board of Directors are classified into three classes of directors; (f) provided that at least two-thirds of the voting power of all of the then-outstanding shares of our capital stock is required to amend the bylaws; (g) provided that stockholders cannot call a special meeting of stockholders, act by written consent without a meeting, fill vacancies in the Board of Directors, remove a director other than for cause, or change the authorized number of directors; and (h) included certain other provisions customary for public companies.
	Equity Incentive Plan and Employee Stock Purchase Plan
	Our Board of Directors adopted the 2012 Equity Incentive Plan, or the 2012 Plan, which became effective on March 12, 2013 and serves as the successor to our 2003 Stock Option Plan, or the 2003 Plan. Pursuant to the 2012 Plan, 3,400,000 shares of our common stock were initially reserved for grant, plus (1) any shares that were reserved and available for issuance under the 2003 Plan at the time the 2012 Plan became effective, and (2) any shares that become available upon forfeiture or repurchase by us under the 2003 Plan and a stock option plan assumed in connection with a previous acquisition, will be reserved for issuance. Under the 2012 Plan, we may grant both incentive and non-statutory stock options, restricted stock and restricted stock units to employees, directors and service providers. We may grant options to purchase shares of common stock to employees, directors and service providers at prices not less than the fair market value at date of grant for both Incentive Stock Options, or ISOs or Nonqualified Stock Options, or NQSOs. ISO options granted to a person who, at the time of the grant, owns more than 10% of the voting power of all classes of stock must be at no less than 110% of the fair market value and expire five years from the date of grant. All other options generally have a contractual term of 10 years. Options generally vest over four years. Restricted stock units, or RSUs generally vest between two to four years.
	Our Board of Directors adopted the 2012 Employee Stock Purchase Plan, or ESPP, which became effective on March 12, 2013, pursuant to which 400,000 shares of our common stock have been reserved for future issuance. Eligible employees can enroll and elect to contribute up to 15% of their compensation through payroll withholdings in each offering period, subject to certain limitations. Each offering period is six months in duration, with the exception of the initial offering period which commenced in March 2013 upon the date our IPO was declared effective and that ended on February 14, 2014. The purchase price of the stock is the lower of 85% of the fair market value on (a) the first day of the offering period or (b) the purchase date.
	As of December 31, 2014 and 2013, there were 4.3 million and 2.5 million shares, respectively, of common stock reserved for future issuance under our 2012 Employee Stock Purchase Plan and future granting under the 2012 Plan.
	Common Stock Warrants
	In March 2011, we granted a warrant to purchase 50,000 shares of common stock at $0.005 per share. The warrant was immediately exercisable and non-forfeitable, and would have expired on the earlier of a change in control or March 31, 2016.
	In connection with our IPO, warrants to purchase shares of our preferred stock converted into warrants to purchase 20,768 shares of our common stock, at a weighted average exercise price of $13.91 per share.
	As of December 31, 2013, we issued 57,370 shares of common stock pursuant to the net exercise of all of our common stock warrants.

StockBased_Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2014
Stock-Based Compensation [Abstract]
Stock-Based Compensation	9. STOCK-BASED COMPENSATION
	We recorded stock-based compensation expense as follows (in thousands):
		Year Ended December 31,
		2014			2013			2012
	Cost of revenue	$	7,610		$	12,275		$	2,553
	Research and development		9,677			17,333			4,229
	Sales and marketing		6,062			7,060			2,822
	General and administrative		10,512			15,836			5,488
	Stock-based compensation expense	$	33,861		$	52,504		$	15,092
	Of the total stock-based compensation, we recorded $0.3 million, $1.6 million, and $0.0 million, respectively as stock-based compensation related to our corporate bonus incentive plan during the years ended December 31, 2014, 2013 and 2012. As of December 31, 2014 and 2013, stock-based bonus of $1.9 million and $1.6 million, respectively, were recorded under accrued liabilities in the consolidated balance sheets in connection with our corporate bonus incentive plan.
	We issue new common shares upon exercise of stock options. The following table summarizes our stock option activity and related information for the year ended December 31, 2014 (in thousands, except per share data):
		Options Outstanding
				Weighted			Weighted
				Average			Average
				Exercise			Remaining		Aggregate
		Number of		Price per			Contractual		Intrinsic
		Shares		Share			Term (years)		Value
	Balance at December 31, 2013	4,726		$	11.88
	Options granted	732			14.67
	Options exercised	-378			2.94
	Options cancelled or expired	-555			17.57
	Balance at December 31, 2014	4,525		$	12.38		5.67		$	8,699
	As of December 31, 2014:
	Options vested and expected to vest	4,454		$	12.32		5.62		$	8,699
	Options exercisable	3,372		$	11.08		4.65		$	8,699
	The aggregate intrinsic value disclosed above represents the total intrinsic value (the difference between the fair value of our common stock as of December 31, 2014 and the exercise price, multiplied by the number of in-the-money options) that would have been received by the option holders had all option holders exercised their options on December 31, 2014.  This amount is subject to change based on changes to the fair value of our common stock. During the years ended December 31, 2014, 2013, and 2012, the total cash received from the exercise of stock options was $1.1 million, $2.9 million, and $0.6 million, net of repurchases, respectively, and the total intrinsic value of stock options exercised was $3.6 million, $9.5 million, and $6.6 million, respectively.
	Restricted Stock Units
	The following table summarizes our restricted stock unit activity and related information for the year ended December 31, 2014 (in thousands, except per share data):
		Restricted Stock
		Units Outstanding
				Weighted
				Average Grant
		Number of		Date Fair Value
		Shares		per Share
	Balance at December 31, 2013	2,757		$	19.14
	Restricted stock units granted	1,218			10.72
	Restricted stock units vested	-1,280			18.77
	Restricted stock units cancelled	-497			17.50
	Balance at December 31, 2014	2,198		$	15.06
	The fair values of restricted stock units are determined based upon the fair value of the underlying common stock at the date of grant.
	Valuation of Employee Stock-Based Compensation
	We recognize compensation expense for stock-based awards based on their grant-date fair value on a straight-line basis over the service period for which such awards are expected to be outstanding. The fair value of stock options granted pursuant to our equity incentive plans is determined using the Black-Scholes-Merton option pricing model. The determination of fair value is affected by the estimates of our valuation, as well as assumptions regarding subjective and complex variables such as expected employee exercise and forfeiture behavior and our expected stock-price volatility over the expected term of the award. Generally, assumptions are based on historical information and judgment was required to determine if historical trends may be indicators of future outcomes. The fair value of each option grant is estimated on the date of grant.
	We currently have no history or expectation of paying cash dividends on our common stock. We estimate the volatility of our common stock at the date of grant based on the historical and implied volatility of the stock prices of a peer group of publicly-traded companies for a period equal to the expected life of our stock options. The risk-free interest rate is based on the U.S. Treasury yield for a term consistent with the expected term of the awards in effect at the time of grant. The expected term represents the weighted-average period the stock options are expected to remain outstanding. The expected term is determined based on historical exercise behavior, post-vesting termination patterns, options outstanding and future expected exercise behavior.
	The following table summarizes the assumptions relating to our stock options:
		Year Ended December 31,
		2014				2013				2012
	Expected volatility		43% - 47	%			47% – 52	%			53.0	%
	Expected dividends		—	%			—	%			—	%
	Expected life in years		6.08				5.00 – 6.08				5.95 – 6.08
	Risk-free interest rate		1.81% - 1.98	%			0.87% – 1.96	%			1.0	%
	Weighted average grant date fair value per share	$	6.60			$	19.11			$	21.20
	The following table summarizes the assumptions relating to our ESPP:
	Expected volatility	33 - 36	%
	Expected dividends	—	%
	Expected life in years	< 1 year
	Risk-free interest rate	0.05 - 0.08	%
	As of December 31, 2014 there was $28.5 million of total unrecognized compensation cost related to non-vested stock-based compensation arrangements, which is expected to be recognized over a weighted-average period of 2.5 years. The total fair value on the respective vesting dates of restricted stock units during the years ended December 31, 2014, 2013 and 2012 was $17.3 million, $19.5 million and $0.3 million, respectively.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Taxes [Abstract]
Income Taxes	10. INCOME TAXES
	The components of loss before income taxes are as follows (in thousands):
		Year Ended December 31,
		2014			2013			2012
	United States	$	-57,125		$	-28,774		$	-73,662
	Foreign		-30,623			-37,809			-15,665
	Loss before income taxes	$	-87,748		$	-66,583		$	-89,327
	The provision (benefit) for income taxes consists of the following (in thousands):
		Year Ended December 31,
		2014			2013			2012
	Current:
	United States federal	$	—		$	—		$	—
	State		1,191			-115			382
	Foreign		613			452			306
	Total current provision for income taxes		1,804			337			688
	Deferred:
	United States federal		—			-47			—
	State		—			123			—
	Foreign		-382			-189			-298
	Total deferred benefit for income taxes		-382			-113			-298
	Provision for income taxes	$	1,422		$	224		$	390
	The provision for income taxes differs from the amount computed by applying the federal statutory income tax rate of 35% to loss before income taxes as follows (in thousands):
		Year Ended December 31,
		2014			2013			2012
	Federal statutory tax expense (benefit)	$	-30,031		$	-23,304		$	-31,265
	Research tax credit		-574			-884			—
	Effect of non-U.S. operations		10,754			13,320			5,469
	Change in valuation allowance		18,166			-925			23,732
	Stock-based compensation expense		1,982			3,455			2,665
	Remeasurement of preferred stock warrant liability		—			—			-752
	Loss on debt extinguishments		—			8,287			—
	Other		1,125			275			541
	Provision for income taxes	$	1,422		$	224		$	390
	Deferred income taxes reflect the tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. The components of our deferred tax assets and liabilities are as follows (in thousands):
		December 31,
		2014			2013
	Deferred tax assets:
	Net operating loss and tax credit carryforwards	$	129,471		$	157,971
	Deferred revenue		159,523			96,054
	Stock-based compensation expense		12,241			11,415
	Warrant liability		—			—
	Accruals and reserves		7,452			5,793
	Intangible assets		1,434			1,480
	Other		355			343
	Gross deferred tax assets		310,476			273,056
	Valuation allowance		-186,273			-168,092
	Deferred tax assets		124,203			104,964
	Deferred tax liabilities
	Property and equipment, net		-1,612			-1,905
	Deferred cost of revenue		-122,116			-102,459
	Deferred tax liabilities		-123,728			-104,364
	Net deferred tax assets	$	475		$	600
	As of December 31, 2014, we had federal and state net operating loss carryforwards of $307.5 million and $315.3 million, respectively. If not utilized, the federal and state net operating loss carryforwards will begin to expire in 2029 and 2015, respectively.  In addition, we had federal and California research tax credit carryforwards of $9.3 million and $10.9 million, respectively. The federal credit carryforwards will begin to expire in 2024, and the California credit carryforwards have no expiration date.
	Since its enactment as part of the Economic Recovery Tax Act of 1981 (ERTA), P.L 97-34, the federal research and development (R&D) tax credit has been available to taxpayers incurring qualifying research expenses (QREs) in the United States. However, the federal R&D tax credit is still not a permanent part of the tax law and must be extended each year by Congress. During 2014, the federal R&D tax credit was extended through the end of December 31, 2014.
	Under Section 382 of the Internal Revenue Code of 1986, as amended, or the Code, our ability to utilize net operating loss carryforwards or other tax attributes, such as research tax credits, in any taxable year may be limited if we experience an “ownership change.” A Section 382 “ownership change” generally occurs if one or more stockholders or groups of stockholders who own at least 5% of our stock increase their ownership by more than 50 percentage points over their lowest ownership percentage within a rolling three-year period. Similar rules may apply under state tax laws. It is possible that an ownership change, or any future ownership change, could have a material effect on the use of our net operating loss carryforwards or other tax attributes, which could adversely affect our operating results.
	Below summarizes the change in deferred tax assets valuation allowance (in thousands):
					Balance at Beginning of Period			Net Change			Balance at End of Period
	Deferred tax assets valuation allowances
		Year ended December 31, 2012		$	141,820		$	25,175		$	166,995
		Year ended December 31, 2013			166,995			1,097			168,092
		Year ended December 31, 2014			168,092			18,181			186,273
	Undistributed earnings of our foreign subsidiaries amounted to $5.6 million as of December 31, 2014. Those earnings are considered to be indefinitely reinvested and, accordingly, no U.S. income taxes have been provided thereon. Upon distribution of those earnings in the form of dividends or otherwise, we would be subject to both U.S. income taxes (subject to an adjustment for foreign tax credits) and foreign withholding taxes. The income tax liability that might be incurred if these earnings were to be distributed is not material to the financial statements because of the Company’s full valuation allowance position.
	A reconciliation of the beginning and ending amounts of unrecognized tax benefits is as follows (in thousands):
		Year Ended December 31,
	2014			2013			2012
Unrecognized tax benefits—beginning of period	$	8,715		$	5,586		$	4,393
Gross increase for tax positions of prior years		165			1,216			774
Gross decrease for tax positions of prior years		-13			—			—
Gross increase for tax positions of current year		1,778			1,913			419
Unrecognized tax benefits balance—end of period	$	10,645		$	8,715		$	5,586
As of December 31, 2014, $0.2 million of the gross unrecognized tax benefits have been recorded as long-term liabilities.  The remainder is reflected as a reduction of deferred tax assets.  Up to $8.7 million and $7.1 million of unrecognized tax benefits at December 31, 2014 and 2013, respectively, would reduce the effective income tax rate in future periods if recognized. However, one or more of these unrecognized tax benefits relate to deferred tax assets that could be subject to a valuation allowance if and when recognized in a future period, which could impact the timing and amount of any related effective tax rate benefit.
We recognize interest and penalties related to uncertain tax positions in income tax expense. To the extent accrued interest and penalties do not ultimately become payable, amounts accrued will be reduced and reflected as a reduction of the provision for income taxes in the period that such determination is made. Due to our net operating loss position, we have not recorded interest and penalties related to uncertain tax positions as of December 31, 2014.
We file income tax returns in the United States, including various states, and certain foreign jurisdictions. The tax years 2002 to 2014 remain open to examination by the major taxing jurisdictions in which we are subject to tax. As of December 31, 2014, we were not under examination by the Internal Revenue Service or any state or foreign tax jurisdiction.

Segment_Information

Segment Information	12 Months Ended
	Dec. 31, 2014
Segment Information [Abstract]
Segment Information	11. SEGMENT INFORMATION
	We operate in one reportable segment. Our chief operating decision maker is our Chief Executive Officer, who reviews consolidated operating results to make decisions about allocating resources and assessing performance for the entire company. Revenue by geography is based on the billing address of the customer. The following table presents revenue by geographic region (in thousands):
		Year Ended December 31,
		2014		2013		2012
	Revenue:
	United States	$	101,579	$	285,430	$	181,948
	Australia		62,745		40,939		13,905
	All Other		26,964		489		884
	Total	$	191,288	$	326,858	$	196,737
	Substantially all of our long-lived assets are located in the United States.

Balance_Sheet_Details

Balance Sheet Details	12 Months Ended
	Dec. 31, 2014
Balance Sheet Details [Abstract]
Balance Sheet Details	12. BALANCE SHEET DETAILS
	Deferred Revenue and Deferred Cost of Revenue
	The following table details the activity in deferred revenue (in thousands):
		Year Ended December 31,
		2014			2013
	Deferred revenue, beginning of period	$	524,653		$	508,056
	Revenue deferred in the period		276,228			343,455
	Revenue recognized in the period		-191,288			-326,858
	Deferred revenue, end of period	$	609,593		$	524,653
	Deferred revenue, current		91,688	—	—	111,293
	Deferred revenue, non-current		517,905	—	—	413,360
	Deferred revenue, end of period	$	609,593		$	524,653
	The following table details the activity in deferred cost of revenue (in thousands):
		Year Ended December 31,
		2014			2013
	Deferred cost of revenue, beginning of period	$	276,123		$	245,163
	Costs deferred related to revenue deferred in the period		123,001			170,213
	Cost of revenue recognized in the period		-66,094			-139,253
	Deferred cost of revenue, end of period	$	333,030		$	276,123
	Deferred cost of revenue, current		29,585	—	—	37,460
	Deferred cost of revenue, non-current		303,445	—	—	238,663
	Deferred cost of revenue, end of period	$	333,030		$	276,123
	Inventory
	Inventory consisted of the following (in thousands):
		December 31,
		2014			2013
	Component parts	$	2,843		$	141
	Finished goods		3,879			4,209
	Inventory	$	6,722		$	4,350
	Finished goods inventory included consigned inventory totaling $3.5 million and $2.8 million as of December 31, 2014 and 2013, respectively.
	Property and Equipment, Net
	Property and equipment, net, consisted of the following (in thousands):
		December 31,
		2014			2013
	Computer and network equipment	$	14,708		$	15,328
	Software		13,460			13,003
	Machinery and equipment		10,538			8,543
	Furniture and fixtures		1,335			929
	Leasehold improvements		2,565			1,161
	Total property and equipment		42,606			38,964
	Less: Accumulated depreciation and amortization		-29,746			-26,600
	Property and equipment, net	$	12,860		$	12,364
	Depreciation and amortization expense associated with property and equipment, including amounts for assets held under capital leases, was $5.9 million, $6.5 million, and $7.1 million for the years ended December 31, 2014, 2013, and 2012, respectively.
	Machinery and equipment included $4.8 million and $6.3 million of assets held under capital leases at December 31, 2014 and 2013, respectively, with corresponding accumulated amortization of $3.5 million and $3.8 million, respectively.
	Software included $3.5 million and $3.0 million of assets held under capital leases at December 31, 2014 and 2013, respectively, with corresponding accumulated amortization of $2.9 and $2.2 million, respectively.
	Accrued Liabilities
	Accrued liabilities consisted of the following (in thousands):
		December 31,
		2014			2013
	Accrued payroll and related expenses	$	8,912		$	10,677
	Accrued operating expenses		2,548			3,949
	Warranty obligations, current		3,838			2,985
	Sales, property and income taxes		1,996			1,202
	Other deferred revenue		4,955			1,994
	Other		1,009			475
	Accrued liabilities	$	23,258		$	21,282
	Other Liabilities
	Other liabilities consisted of the following (in thousands):
		December 31,
		2014			2013
	Warranty obligations, non-current	$	3,397		$	3,104
	Other deferred revenue		9,816			9,174
	Other		1,861			1,961
	Other liabilities	$	15,074		$	14,239
Product Warranty
Product warranty obligation is presented as follows on the consolidated balance sheets (in thousands):
	December 31,
	2014			2013
Warranty obligation, current—classified in accrued liabilities	$	3,838		$	2,985
Warranty obligation, non-current—classified in other liabilities		3,397			3,104
	$	7,235		$	6,089
Product warranty activity was as follows (in thousands):
	Year Ended
	December 31,
	2014				2013		2012
Warranty obligation—beginning of period	$	6,089		$	6,316		$	9,631
Warranty expense for new warranties issued		669			1,406			1,372
Utilization of warranty obligation		-2,562			-1,767			-2,671
Changes in estimates for pre-existing warranties		3,039			134			-2,016
Warranty obligation—end of period	$	7,235		$	6,089	—	$	6,316
During the years ended December 31, 2014 and 2013, we revised our estimated warranty liability to reflect updated product field reliability experience and recorded an increase of product warranty liability and product cost of revenue by $3.0 million and $0.1 million, respectively. The change in estimates in fiscal 2014 is primarily due to increase in warranty disposition and processing cost.
As of December 31, 2014 and 2013, we had deferred revenue related to arrangements with extended warranty of $582,000 and $206,000, respectively, included in other deferred revenue under accrued liabilities, and $8.8 million and $7.1 million, respectively, included in other deferred revenue under other liabilities above.
Accumulated Other Comprehensive Income (AOCI)
The components of AOCI, net of tax, were as follows (in thousands):
	Foreign Currency			Unrealized Gains
	Translation			on Available for
	Adjustments			Sale Securities			Total
Balance as of December 31, 2013	$	46		$	84		$	130
Other comprehensive income (loss) before reclassification		-770			-11			-781
Amounts reclassified from AOCI		—			-128			-128
Other comprehensive income		-770			-139			-909
Balance as of December 31, 2014	$	-724		$	-55		$	-779

Borrowings

Borrowings	12 Months Ended
	Dec. 31, 2014
Borrowings [Abstract]
Borrowings	13. BORROWINGS
	Credit Facility
	We have available a line of credit with a bank, which originally provided for advances and the issuance of letters of credit of up to $40 million. On May 8, 2013, we amended our credit agreement to increase the available capacity from $40 million to $50 million. Loans under the credit agreement bear interest at the bank’s prime rate plus a margin. The credit agreement is guaranteed by certain of our accounts receivable, inventory and cash. As of December 31, 2014, there were no borrowings outstanding under the credit agreement; however, $17.0 million of letters of credit were outstanding, including $13.0 million relating to EON Patent Litigation as discussed under Note 16, Commitments and Contingencies. The remaining available balance of $33.0 million under line of credit is available for cash borrowings or additional letters of credit, subject to compliance with financial covenants and other customary conditions to borrowings.
	The credit agreement will terminate and all amounts owing thereunder will be due and payable on May 17, 2015, unless (a) the commitments are terminated earlier, either at our request or, if an event of default occurs, by the bank (or automatically in the case of certain bankruptcy-related events of default), or (b) the maturity date is extended upon our request, subject to the agreement of the bank. The credit agreement contains customary representations, warranties, affirmative and negative covenants, including financial covenants, events of default and indemnification provisions in favor of the bank. The negative covenants include restrictions regarding the incurrence of liens, subject to certain exceptions. The financial covenants require us to meet monthly financial tests with respect to liquidity ratio and unrestricted cash. As of December 31, 2014 we were in compliance with the financial covenants in the credit agreement.
	Subordinated Convertible Notes
	In December 2011, we issued the December 2011 Note for an aggregate principal amount of $24.0 million, with a maturity date of December 6, 2014. Interest accrued for the first six months at a rate of 3.0% per year and increased by 1.0% every six months to a maximum of 6.0% per year. In February 2012, we issued the February 2012 Note for an aggregate principal amount of $30.0 million, with a maturity date of February 21, 2015. Interest accrued for the first six months at a rate of 3.0% per year and increased by 1.0% every six months to a maximum of 6.0% per year. The unpaid principal amount of the December 2011 Note and February 2012 Note, together with any interest accrued but unpaid thereon, were convertible upon certain events, including closing of an IPO of our common stock.
	In connection with our IPO, the December 2011 Note and February 2012 Note together with contractual accrued interest of $2.3 million thereon through March 18, 2013, the closing date of our IPO, converted into 3,764,954 shares of common stock based on the outstanding principal and accrued interest at a conversion price equal to 88% of the IPO price of $17.00 per share. The conversion of the convertible notes and issuance of common stock were accounted for as debt extinguishments and as a result, we recorded a loss on debt extinguishments of $22.9 million in the year ended December 31, 2013.

Benefit_Plan

Benefit Plan	12 Months Ended
	Dec. 31, 2014
Benefit Plan [Abstract]
Benefit Plan	14. BENEFIT PLAN
	In 2003, our Board of Directors approved the adoption of a savings plan under Section 401(k) of the Internal Revenue Code of 1986, as amended (the “Code”). The plan covers eligible employees who elect to participate. We are allowed to make discretionary profit sharing and qualified non-elective contributions as defined by the Plan and as approved by the Board of Directors. We have not historically matched eligible participants’ 401(k) contributions. No discretionary profit sharing contributions have been made to date.

Restructuring

Restructuring	12 Months Ended
	Dec. 31, 2014
Restructuring [Abstract]
Restructuring	15. RESTRUCTURING
	2014 Restructuring Plan
	During the three months ended September 30, 2014, we initiated a restructuring plan (the “2014 Restructuring Plan”) to refocus our strategy, optimize our structure, and improve operational efficiencies. The 2014 Restructuring Plan included a worldwide workforce reduction. As a result, we recorded $1.8 million in severance costs as restructuring charges during the year ended December 31, 2014 in the consolidated statement of operations.  Any changes in the estimates of executing the approved plans are reflected in our results of operations.
	In connection with the 2014 Restructuring Plan, we expect to record aggregate future charges of approximately $1.6 million to $2.1 million of additional severance.  The remaining restructuring costs under the 2014 Restructuring Plan are expected to be incurred by the first half of 2015.
	Accrued liabilities related to restructuring actions during 2014 consist of the following (in thousands):
		Year Ended December 31,
		2014
		Severance Costs
	Balance—December 31, 2013	$	—
	Additions during the period		1,888
	Utilization during the period		-1,653
	Balance—December 31, 2014	$	235

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies [Abstract]
Commitments and Contingencies	16. COMMITMENTS AND CONTINGENCIES
	Operating and Capital Leases
	Our primary operating lease commitment at December 31, 2014, related to our headquarters in Redwood City, California, requires monthly lease payments through December 2016. We recognize rent expense on a straight-line basis over the lease period. Where leases contain escalation clauses, rent abatements, or concessions, such as rent holidays and landlord or tenant incentives or allowances, we apply them in the determination of straight-line rent expense over the lease term. Rent expense for all facility leases was $5.3 million, $4.9 million, and $4.0 million for the years ended December 31, 2014, 2013 and 2012, respectively.
	In March 2012 and June 2012, we sold assets to a financial institution. Concurrently with the sales, we entered into separate agreements to lease the property back from the financial institution over a minimum lease term of three years. The subsequent leasebacks qualified as normal leasebacks and are classified as capital leases. The gains and losses on the transactions were not material.
	The following table provides a summary of the sale leaseback transactions that were outstanding as of December 31, 2014 (in thousands):
				Term		Interest	Financed
	Lease Commencement		Lease Termination	(months)		rate	Amount
	March 2012		March 2015	36		7.4		716
	June 2012		June 2015	36		6.7		960
							$	1,676
	As of December 31, 2014, the future minimum commitments under our operating and capital leases were as follows (in thousands):
		Operating		Capital
		Leases		Leases
	2015	$	5,507	$	1,163
	2016		4,354		112
	2017		614		—
	2018		624		—
	2019		562		—
	2020 and thereafter		1,489		—
	Net minimum lease payments	$	13,150	$	1,275
	Less amount representing interest				-50
	Present value of net minimum capital lease payments			$	1,225
	Legal Contingencies
	EON Patent Litigation.  In June 2011, EON Corp. IP Holdings, LLC, a non-producing entity, or EON, filed suit in United States District Court for the Eastern District of Texas, Tyler Division against us and a number of smart grid providers.  The lawsuit alleges infringement of United States Patent Nos. 5,388,101 (the “’101 Patent”), 5,481,546 (the “’546 Patent”), and 5,592,491 (the “’491 Patent,” and together with the ‘101 Patent and the ‘546 Patent, the “EON Patents”) by certain networking technology and services that we and the other defendants provide.  Other defendants included Landis+Gyr AG, Aclara Power-Line Systems Inc., Elster Solutions, LLC, Itron, Inc. and Trilliant Networks Inc., all of which settled with EON prior to trial. We filed answers, affirmative defenses and counterclaims denying the plaintiff’s allegations and asserting that the plaintiff’s patents are invalid.  A trial was held in June 2014.  After the trial, the jury determined that we had infringed certain, but not all, of the claims under the EON Patents, and returned a verdict against us in the amount of $18.8 million.  The court ruled there was insufficient evidence to support EON’s allegation of willful infringement and granted our motion to dismiss that claim.  In June 2014, we filed post-trial motions with the court seeking, among other things, judgment as a matter of law to set aside the jury verdict, or in the alternative, a new trial.  In its post-trial motions, EON sought pre-judgment interest and attorneys’ fees.  Following post-trial motions, the court reduced the damage award to approximately $13.0 million, and in December 2014, entered a final judgment in that amount plus approximately $1.5 million in pre-judgment interest.  The court subsequently revised the final judgment to include additional costs of about $0.2 million and entered an amended final judgment in December 2014.  All of the EON Patents have expired and therefore EON is not seeking, and EON may not recover, any additional sums as royalties for our sales of products going forward.
	In December 2014, we filed a notice of appeal with the U.S. Court of Appeals for the Federal Circuit in Washington, D.C.  In order to stay the execution of the final judgment pending the appeal, in December 2014 we filed a surety bond in the amount of $17.6 million, which includes an additional 20% of the final judgment for post-judgment interest and expenses expected to be incurred during the appeal process, in accordance with court rules.  The bond was issued by Zurich Insurance and is collateralized with a standby letter of credit in the amount of $13.0 million, the amount of the damage award, as stated in Note 13, Borrowings.  Upon completion of the appeal process, both the surety bond and standby letter of credit will be released.  In January 2015, the District Court accepted the bond and entered the stay of execution of the judgment.  EON filed a notice of cross appeal in January 2015.  Our opening appellate brief is due in March 2015.  We expect the appeal process to take place during 2015 and perhaps into early 2016.
	We continue to believe that the evidence and the law do not support the jury’s findings of infringement, validity, and the award of damages, and intend to continue vigorously defending the action, including exercising all available appeals.  However, given the inherent uncertainty in predicting the ultimate outcome of the appeals process, we believe it is reasonably possible that a material loss of up to $14.7 million, the amount of the amended final judgment, may result from these proceedings.  In continuing to assess the impact of the jury verdict and the judgment on our financial statements, we will continue to evaluate the jury verdict, the court’s rulings on the post-trial motions and the likelihood of a successful appeal.
	Transdata/OG&E Patent Litigation.  In September 2011, TransData, Inc., or TransData, filed suit in United States District Court for the Western District of Oklahoma, against Oklahoma Gas & Electric Company (“OG&E”), alleging infringement of United States Patent Nos. 6,181,294, 6,462,713, and 6,903,699 by certain wireless communication-enabled meters, including General Electric Company (“GE”) meters with our wireless modules.  We have agreed with GE to contribute to pay the defense of OG&E in connection with the TransData suit. An early claim construction hearing was held regarding one claim term in February 2013, and a hearing for the full claim construction was held in September 2013, on which the court issued an order in October 2013.  In May 2014, GE filed reexamination requests on the TransData patents at issue with the U.S. Patent and Trademark Office (the “USPTO”).  The reexaminations are currently proceeding.  In August and September 2014, GE also petitioned the USPTO for inter partes review of each patent.  In October 2014, OG&E filed a motion to stay the litigation pending the reexamination of the patents by the USPTO, which the court denied in January 2015.  Pre-trial proceedings in the matter are ongoing.  We believe that OG&E has meritorious defenses to TransData’s allegations, and that OG&E will continue to vigorously defend itself.
	Linex Patent Litigation.  In March 2013, Linex Technologies, Inc., a non-producing entity, or Linex, filed suit against us in United States District Court for the Southern District of Florida. Linex alleged that certain of our networking technology infringes United States Patent Nos. 6,493,377 and 7,167,503. We filed an answer in May 2013. In January 2014, the court granted the plaintiff’s request for a stay of the matter, pending reexamination of the patents at issue by the USPTO. In September 2014, Linex amended certain patent claims and canceled certain other patent claims based upon the USPTO’s completed reexaminations, and in October 2014, the court lifted the stay of the matter.  In January 2015, Linex filed an amended complaint to incorporate facts related to the reexamination, and we filed an answer responding to the complaint and raising additional defenses.  The trial has been scheduled for November 2015.  We believe that we have meritorious defenses to Linex’s allegations and intend to continue vigorously defending against the action.
	We have not recorded any amounts for contingent losses associated with the matters described above based on its belief that losses, while reasonably possible, are not probable.  Unless otherwise stated, we are currently unable to predict the final outcome of these lawsuits and therefore cannot determine the likelihood of loss nor estimate a range of possible loss.
	We are directly involved with various unresolved legal actions and claims, and are indirectly involved with proceedings by administrative bodies such as public utility commissions, arising in the ordinary course of business.  We do not believe that any liability from any reasonably foreseeable disposition of such legal actions and claims, individually or in the aggregate, would have a material effect on our consolidated financial statements.  There are many uncertainties associated with any litigation or claim, and we cannot be certain that these actions or other third-party claims will be resolved without costly litigation, fines and/or substantial settlement payments.  If that occurs, our business, financial condition and results of operations could be materially and adversely affected.  If information becomes available that causes us to determine that a loss in any of our pending litigation matters, claims or settlements is probable, and a reasonable estimate of the loss associated with such events can be made, we will record the estimated loss at that time.
	Customer Performance and Other Commitments
	Certain customer agreements require us to obtain letters of credit or surety bonds in support of our obligations under such arrangements. These letters of credit or surety bonds typically provide a guarantee to the customer for future performance, which usually covers the deployment phase of a contract and may on occasion cover the operations and maintenance phase of service contracts.
	As of December 31, 2014 and 2013, we had a total of $17.0 million, including $13.0 million related to EON Patent Litigation mentioned above, and $9.8 million, respectively, of standby letters of credit issued under the credit facility with a financial institution, of which $0.5 million (AUD$0.6 million) and $0.6 million (AUD$0.6 million), respectively, were denominated in Australian dollars. In accordance with the terms of our credit facility, increases or decreases in the exchange rate between the Australian dollar and the U.S. dollar will increase or decrease the amount available to us under the credit facility.
	As of December 31, 2014, we had a $20.3 million unsecured surety bond. The surety bond provides a financial guarantee to support performance obligations under certain customer agreements. As of December 31, 2013, we had a $15.0 million unsecured surety bond. The surety bond provides a financial guarantee to support performance obligations under certain customer agreements. In the event any such letters of credit or surety bonds are called, we would be obligated to reimburse the issuer of the letter of credit or surety bond. We do not believe there will be any claims against currently outstanding letters of credit or surety bonds.
	Indemnification Commitments
	Directors, Officers and Employees. In accordance with our bylaws and/or pursuant to indemnification agreements we have entered into with directors, officers and certain employees, we have indemnification obligations to our directors, officers and employees for claims brought against these persons arising out of certain events or occurrences while they are serving at our request in such a capacity. We maintain a director and officer liability insurance coverage to reduce our exposure to such obligations, and payments made under these agreements. To date, there have been no indemnification claims by these directors, officers and employees.
	Customers and Third Party Device Manufacturers. Refer to the discussion above under the heading Legal Contingencies for a description of our indemnification obligations.
	Our contracts with customers and third party device manufacturers typically provide indemnification for claims filed by third parties alleging that our products and services sold to the customer or manufacturer infringe or misappropriate any patent, copyright, trademark or other intellectual property right.
	In our customer contracts, we also typically provide an indemnification for third-party claims resulting from death, personal injury or property damage caused by the negligence or willful misconduct of our employees and agents in connection with the performance of certain contracts.
	Under our customer and third party device manufacturer indemnities, we typically agree to defend the utility customer or third party device manufacturer, as the case may be, from such claims, and pay any resulting costs, damages and attorneys’ fees awarded against the indemnified party with respect to such claims, provided that (a) the indemnified party promptly notifies us in writing of the claim, (b) the indemnified party provides reasonable assistance to us at our expense, and (c) we have sole control of the defense and all related settlement negotiations.
	Insurance.  We maintain various insurance coverages, subject to policy limits, that enable us to recover a portion of any amounts paid by us in connection with our obligation to indemnify our customers and third party device manufacturers. However, because our maximum liability associated with such indemnification obligations generally is not stated explicitly in the related agreements, and further because many states prohibit limitations of liability for such indemnified claims, the maximum potential amount of future payments we could be required to make under these indemnification provisions could significantly exceed insurance policy limits.
	Historically, payments made by us under these indemnification provisions have not had a material effect on our results of operations, financial position or cash flows.

Subsequent_Events

Subsequent Events	12 Months Ended
	Dec. 31, 2014
Subsequent Events [Abstract]
Subsequent Events	17. SUBSEQUENT EVENTS
	On January 16, 2015, we completed the acquisition of Detectent, Inc. (“Detectent”), a privately held corporation that provides customer intelligence solutions for utilities leveraging its data analytics platform. Based in Escondido, California, Detectent’s SaaS, subscription, and software solutions help improve advanced metering infrastructure and utility grid operations, ensure revenue protection, and deliver enhanced customer engagement programs. In accordance with the Agreement and Plan of Merger dated as of January 6, 2015, by and among Silver Spring, Detectent and a wholly-owned subsidiary of Silver Spring, Detectent became our wholly-owned subsidiary. The total purchase consideration was $11.7 million, including $7.7 million of cash and $4.0 million of deferred cash consideration paid over a two-year period subject to key employee retention.   Part of the purchase consideration, $0.3 million represented cash payment (without interest) to the holders of Detectent’s vested stock options.
	The acquisition is being accounted for under the acquisition method of accounting under ASC 805. Under this method of accounting, the total purchase consideration will be measured at fair value as of the acquisition date when control was obtained. Due to the short period of time between the acquisition date and filing of our Annual Report on Form 10-K with the SEC, the acquisition-date fair value of the total consideration transferred and measurement of the assets acquired and liabilities assumed has not been finalized. We are is in the process of obtaining a third-party valuation report to calculate the fair value of the consideration transferred and to measure the assets acquired and liabilities assumed. It is expected that a significant amount of goodwill will be recorded as of the acquisition date. As a result of the acquisition of Detectent, revenues and operating expenses of the Detectent business will be included in our consolidated financial results, beginning in the first quarter of 2015.

Selected_Quarterly_Financial_D

Selected Quarterly Financial Data	12 Months Ended
	Dec. 31, 2014
Selected Quarterly Financial Data [Abstract]
Selected Quarterly Financial Data	18. SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED)
	The following tables set forth selected unaudited quarterly statements of operations data for each of the last eight quarters in the years ended December 31, 2014 and 2013 (in thousands, except per share data).
		Three Months Ended
		December 31,		September 30,		June 30,		March 31,		December 31,		September 30,		June 30,		March 31,
		2014		2014		2014		2014		2013		2013		2013		2013
	Revenue, net	$	77,411	$	28,041	$	41,607	$	44,229	$	97,164	$	72,481	$	103,510	$	53,703
	Cost of revenue		47,233		26,738		28,195		32,785		63,420		49,255		55,260		43,569
	Gross profit		30,178		1,303		13,412		11,444		33,744		23,226		48,250		10,134
	Operating expenses		28,786		38,723		38,084		38,615		33,792		35,341		38,268		49,708
	Operating income (loss)		1,392		-37,420		-24,672		-27,171		-48		-12,115		9,982		-39,574
	Other income (expense), net		68		7		85		-37		138		-54		-184		-24,728
	Income (loss) before income taxes		1,460		-37,413		-24,587		-27,208		90		-12,169		9,798		-64,302
	Provision for income taxes		959		-140		4		599		-268		100		328		64
	Net income (loss)		501		-37,273		-24,591		-27,807		358		-12,269		9,470		-64,366
	Deemed dividend to convertible preferred stockholders		—		—		—		—		—		—		—		-105,000
	Net income (loss) attributable to common stockholders	$	501	$	-37,273	$	-24,591	$	-27,807	$	358	$	-12,269	$	9,470	$	-169,366
	Net income (loss) per share attributable to common stockholders:
	Basic	$	0.01	$	-0.77	$	-0.51	$	-0.58	$	0.01	$	-0.26	$	0.20	$	-16.18
	Diluted	$	0.01	$	-0.77	$	-0.51	$	-0.58	$	0.01	$	-0.26	$	0.19	$	-16.18
	Weighted average shares used to compute net income (loss) per share attributable to common stockholders:
	Basic	$	48,929	$	48,551	$	48,315	$	47,693	$	47,198	$	46,729	$	46,599	$	10,469
	Diluted	$	50,191	$	48,551	$	48,315	$	47,693	$	49,603	$	46,729	$	48,995	$	10,469

Description_of_Business_and_Su1

Description of Business and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
Fair Value Measurements [Abstract]
Basis Of Presentation	The consolidated financial statements and accompanying notes have been prepared in accordance with accounting principles generally accepted in the United States, or GAAP. The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. Intercompany balances and transactions have been eliminated in consolidation.
Use of Estimates	Use of Estimates
	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and the accompanying notes during the reporting period. Estimates are used for revenue and cost recognition, inventory valuation, warranty obligations, stock-based compensation, valuation of assets acquired and liabilities assumed in a business combination, classification of current and non-current deferred revenue and deferred cost of revenue, income taxes and deferred income tax assets and associated valuation allowances. These estimates generally involve complex issues and require judgments, involve the analysis of historical and prediction of future trends, can require extended periods of time to resolve and are subject to change from period to period. Actual results may differ materially from management’s estimates.
Cash, Cash Equivalents and Short-term Investments	Cash, Cash Equivalents and Short-term Investments
	Cash equivalents consist of highly liquid investments with insignificant interest rate risk and original maturities at the time of purchase of three months or less, and consist of money market funds. Short-term investments consist of high grade investment securities with original maturities at the time of purchase of greater than three months, and are available for use in current operations. We classify all of our cash equivalents and short-term investments as available-for-sale, which are recorded at fair value. Unrealized gains and losses are included in accumulated other comprehensive income (loss) in stockholders’ deficit. Realized gains and losses are included in other income and expense, net. We evaluate our short-term investments for impairment each reporting period. Determining whether a decline in fair value is other-than-temporary requires management judgment based on the specific facts and circumstances of each security. We consider various factors in determining whether to recognize an impairment charge, including the length of time the investment has been in a loss position, the extent to which the fair value has been less than the our cost basis, the investment's financial condition, and near-term prospects of the investee. If we determine that the decline in an investment's fair value is other than temporary, the difference is recognized as an impairment loss in its consolidated statements of operations. Amounts are reclassified out of accumulated other comprehensive income (loss) into earnings using the specific identification method
Inventory	Inventory
	Inventory is stated at the lower of cost or market. Cost is computed using standard cost, which approximates actual cost on a first-in, first-out basis. The determination of market value involves numerous judgments including estimated average selling prices based upon recent sales volumes, industry trends, existing customer orders and current contract prices. We evaluate our ending inventories for excess quantities and obsolescence based on forecasted demand within specific time horizons, technological obsolescence, and an assessment of any inventory that is not of saleable condition. Forecasted demand requires management estimates and is subject to several uncertainties including market and economic conditions, technology changes and new product introductions. Actual demand may differ from forecasted demand, and such differences may have a material effect on recorded inventory values and operating results.
	In addition, we enter into purchase commitments with third-party contract manufacturers to manage lead times and meet product forecasts and with other parties to purchase various key components used in the manufacture of our products. Accruals are established for estimated losses on purchased components for which we believe it is probable that they will not be recoverable in future operations. To the extent that such forecasts are not achieved, commitments and associated accruals may change.
Revenue Recognition	Revenue Recognition
	We generally market our products and services for our advanced metering, distribution automation and demand-side management solutions directly to customers. For our advanced metering solution, we contract with third-party device manufacturers, which integrate our communications modules into their meters. Our advanced metering solution, which includes our UtilOS network operating system, UtilityIQ software suite, networking hardware, and communications modules, provides utilities with two-way communication from our communications modules to the utility’s back office. Our hardware devices include UtilOS embedded software, which functions together with the tangible hardware elements to deliver the tangible products’ essential functionality. Our UtilityIQ software suite of products includes software that is not embedded with the tangible hardware elements, but that is also necessary to deliver the tangible products’ essential network functionality, as well as other application software that provides additional functionality to the network solution. We derive revenue from sales of products, including hardware and software, as well as services, including network design and deployment support, managed services and SaaS, and ongoing customer support. We enter into separate arrangements with third-party device manufacturers to integrate our communications modules with their meters pursuant to our customers’ specifications. While we may receive payment directly from these third-party device manufacturers, the timing of revenue recognition related to communications modules delivered to third-party device manufacturers is ultimately determined based upon acceptance by our customers. Substantially all of our sales of communications modules have been fulfilled through third-party device manufacturers in this manner.
	We enter into multiple deliverable arrangements with customers to deploy our networking platform and solutions, which include the delivery of hardware and software, as well as services.
	Judgment is required in determining the separate units of accounting, which depends on whether the delivered items have standalone value to customers. When we sell our products and services separately, or when the customer could resell them on a standalone basis, we treat the delivered elements as having standalone value. In our typical customer arrangements, we consider the following to be separate units of accounting: (i) our hardware together with the related embedded software; (ii) our network management software within our UtilityIQ suite that provides the tangible product’s essential network functionality and related hardware for which the network management software is intended to be used; (iii) other application software within our UtilityIQ suite not essential for the customer to obtain functionality of the hardware; and (iv) our service offerings, which include professional services, managed services and SaaS, and ongoing customer support. We determine total arrangement consideration, and exclude amounts that are contingent upon the delivery of additional items or meeting other specified performance conditions, including potential refunds or penalty provisions. We allocate the total arrangement consideration to the deliverables based on our determination of the units of accounting and their relative selling prices. As we have not yet established vendor-specific objective evidence, or VSOE, or identified third-party evidence of fair value for these units of accounting, we use our best estimate of selling price to perform the relative fair value allocation. Judgment is also required in determining how to measure and allocate arrangement consideration among the separate units of accounting. The process for performing an assessment of our best estimate of selling price for our products and services is based on quantitative and qualitative aspects of multiple factors. These factors include market conditions, such as competitive alternatives and pricing practices, as well as company-specific factors, such as standalone sales, nature and size of the customer, contractually stated prices, costs to manufacture products or provide services and profit objectives. In establishing such profit objectives, we consider prices in previous contracts, size of the transaction, and the drivers, if any, that could influence future margins.
	The following revenue recognition criteria are applied to the units of accounting in all utility customer arrangements, as well as those in which orders of communications modules are fulfilled through third party device manufacturers as described above. We do not recognize revenue for a unit of accounting until all of the following criteria have been met:
		·		Persuasive evidence of an arrangement exists. Binding contracts or purchase orders are used to determine the existence of an arrangement.
		·		Delivery has occurred. Shipping documents and customer acceptance provisions, where applicable, are used to verify delivery.
		·		The fee is fixed or determinable. We assess whether the fee is fixed or determinable based on the payment terms associated with the transaction and whether the sales price is subject to refund or adjustment.
		·		Collectibility is reasonably assured. We assess collectibility based primarily on creditworthiness of the customer or third party device manufacturer as determined by credit assessments and payment history.
	Substantially all of our customer arrangements include acceptance provisions that require testing of the network against specific performance criteria. We consider the following factors in our assessment of whether the acceptance provisions are substantive:
		·		whether the criteria are based on our standard performance criteria or are customer-specific;
		·		if the criteria are customer-specific, availability of objective and sufficient evidence to  reliably demonstrate that the delivered products and services will meet all of the specified criteria prior to receipt of customer acceptance;
		·		our experience with similar types of arrangements or products, as well as our experience with the specific customer;
		·		whether we would be successful in enforcing a claim for payment even in the absence of acceptance confirmation from the customer;
		·		the nature and complexity of the acceptance testing, including the planned duration of the acceptance period; and
		·		the significance of financial penalties, if any, associated with not meeting performance criteria.
	Considering our limited historical experience, we have concluded for our current arrangements with acceptance terms, revenue is not recognized until we have determined acceptance is achieved. Once we have achieved acceptance, we recognize revenue as follows:
		·		Revenue from software that functions together with the tangible hardware elements to deliver the tangible products’ essential functionality is recognized upon delivery of both the software and related hardware elements, assuming all other revenue recognition criteria are met.
		·		Application software and related post contract support services which are not considered essential to the functionality of hardware devices are within the scope of ASC 985-605.  In accordance with ASC 985-605, revenues are recognized ratably over the longest service period for post-contract customer support, or PCS, and professional services as we have not established VSOE for software or the related software elements.
		·		Revenue from our service offerings, including professional services such as network design and deployment support, managed services and SaaS, and ongoing customer support is recognized as services are delivered or on a proportional performance basis depending on the underlying pattern of performance.
		·		Revenue from hardware is recognized when title transfers.
	Amounts that are invoiced prior to a transaction meeting all of the above revenue recognition criteria, including customer acceptance criteria, are recorded in deferred revenue until such criteria are satisfied. For all periods presented herein, the amount and timing of revenue and product cost recognition has been, and for the near-term will be, dependent primarily on our ability to meet substantive customer acceptance criteria. We consider a variety of factors in estimating the timing of customer acceptance, which includes contractual milestones, project schedules, availability of resources, the nature and extent of remaining testing cycles, and other relevant information provided by our project management team. Accordingly, we expect that the timing of recognition of revenue and related product costs on both a quarterly and annual basis will not be easily predictable. In addition, it is possible that the amount of current deferred revenue and related deferred cost of revenue reflected as of a balance sheet date will be significantly higher or lower than the amount of deferred revenue and related deferred cost of revenue that is ultimately recognized as revenue and cost of revenue within the 12 months following the balance sheet date. We classify deferred revenue and deferred cost of revenue that we expect to recognize during the 12 months following the balance sheet date as current deferred revenue and current deferred cost of revenue on our balance sheet and the remainder as non-current deferred revenue and non-current deferred cost of revenue.
	Certain of our customer and third-party device manufacturer contracts include contingency provisions, which impact our revenue recognition as such contingent amounts limit the amount of the total arrangement consideration under multiple deliverable contracts that can be allocated to delivered and accepted products and services. Amounts that are invoiced prior to a transaction meeting all of the revenue recognition criteria, including contingency provisions, are recorded in deferred revenue until such provisions have lapsed. For the years ended December 31, 2014 and 2013, such amounts were $26.2 million and $45.8 million, respectively, related to those customers whose revenue which we have started recognizing. These contingencies are related to potential penalties for late delivery, liquidated damages related to failure to meet milestones or deliver specified products or services, or credits to be issued upon the failure to meet service level arrangements. The amounts that could be paid under these provisions are typically limited and capped at amounts that do not exceed the maximum contract value. Accordingly, even in situations where we have received customer acceptance, we limit the revenue recognized for accepted products and services by the amount that could be paid under these provisions. We do not recognize these deferred amounts until the provisions have lapsed.  Predicting when such provisions will lapse is subject to significant uncertainty as the timing is dependent on a variety of factors, including the progress and completion of deployments. Related to the contingency provisions described above, $4.6 million and $13.8 million, respectively, were recorded as current deferred revenue and $21.6 million and $31.9 million, respectively, were recorded as non-current revenue as of December 31, 2014 and 2013.
	In cases where we sell third-party products and services such as meters, hardware, services, software or software maintenance as part of the overall solution, we evaluate whether we act as principal or agent under the arrangement. The evaluation considers multiple factors, including whether we are the primary obligor under the arrangement with the customer, whether we bear the risk of loss and credit risk associated with the supply of third-party products and services, whether we have the ability to change the product or perform part of the service, and whether we have the ability to control the price charged to our customers for the third-party products and services. Revenue is presented on a gross basis when we conclude that we are the principal under the arrangement with respect to third-party products and services, and revenue is presented on a net basis when we conclude that we are acting as the agent. Substantially all of our revenue related to third-party products and services is recognized on a gross basis as we are generally acting as the principal under our arrangements.
	Shipping charges billed to customers were not significant for the years ended December 31, 2014, 2013, and 2012. Shipping charges are included in revenue, and the related shipping costs are included in cost of revenue in the accompanying consolidated statements of operations.
Cost of Revenue	Cost of Revenue
	Cost of revenue consists of cost of product and service revenue. Cost of product revenue includes contract manufacturing costs, including raw materials, components and associated freight, and normal yield loss. In addition, cost of product revenue includes compensation, benefits and stock-based compensation provided to our manufacturing personnel, overhead and other direct costs. Product costs are deferred upon shipment and are recognized in the period in which we recognize the related revenue. Period costs, which consist primarily of logistics costs, manufacturing ramp-up costs, expenses for inventory obsolescence, standard warranty costs and lower of cost or market adjustments are recognized in the period in which they are incurred.
	Costs of providing services include personnel-related costs, depreciation and amortization, and software hosting costs. Costs of providing services are not deferred and are included in cost of revenue in the period in which they are incurred.
Deferred Revenue and Deferred Cost of Revenue	Deferred Revenue and Deferred Cost of Revenue
	Deferred revenue results from transactions where we have billed the customer for product shipped or services performed but all revenue recognition criteria have not yet been met.
	Deferred cost of revenue is recorded for products for which ownership (typically title and risk of loss) has transferred to the customer, but for which criteria for revenue recognition have not been met. We only defer tangible direct costs associated with hardware products delivered. Cost of revenue for providing services is not deferred, but is expensed in the period incurred. Deferred cost of revenue associated with deferred product revenue is recorded at the standard inventory cost at the time of shipment. We evaluate deferred cost of revenue for recoverability based on multiple factors, including whether net revenues less related direct costs will exceed the amount of deferred cost of revenue based on the terms of the overall arrangement. To the extent that deferred cost of revenue is determined to be unrecoverable, we adjust deferred cost of revenue with a charge to product cost of revenue in the current period. In connection with our recoverability assessments, we have not incurred significant impairment charges through December 31, 2014.
	We recognize deferred revenue and associated deferred cost of revenue in the consolidated statements of operations once all revenue recognition criteria have been met.
Product Warranty	Product Warranty
	We provide warranties for substantially all of our products. Our standard warranty period extends from one to five years. We accrue for costs of standard warranty at the time of product shipment, and record changes in estimates to warranty accruals when it is probable a liability has been incurred and the amount of loss can be reasonably estimated.
	At the time of product shipment, we estimate and accrue for the amount of standard warranty cost and record the amount as a cost of revenue. Determining the amount of warranty costs requires management to make estimates and judgments based on historical claims experience, industry benchmarks, test data and various other assumptions including estimated field failure rates that are believed to be reasonable under the circumstances. The amount of warranty costs accrued are net of warranty obligations to be fulfilled by our suppliers. The results of these judgments formed the basis for our estimate of the total charge to cover anticipated customer warranty, repair, return and replacement and other associated costs. Should actual product failure rates, claim levels, material usage or supplier warranties on parts used in our products differ from our original estimates, revisions to the estimated warranty liability could result in adjustments to our cost of revenue in future periods.
	Certain of our standard product warranty obligations require us to reimburse a customer for installation and other related costs in the event that field reliability rates fall below contractually specified thresholds. We consider the probability that we will have to pay such incremental warranty costs based on the expected performance of a delivered product when we record new warranty obligations issued in a period as well as when we determine if any changes are required to our original estimates for pre-existing warranty obligations.
	Our warranty obligations are affected by product failure rates, claims levels, material usage and supplier warranties on parts included in our products. Because our products are relatively new and we do not have the benefit of long-term experience observing products’ performance in the field, it is possible that the estimates of a product’s lifespan and incidence of claims could vary from period to period.
	In certain customer arrangements, we have provided extended warranties for periods of up to 15 years following the initial standard warranty period. We recognize revenue associated with extended warranties over the extended warranty period when the extended warranty period commences. Costs associated with providing extended warranties are expensed as incurred during the extended warranty period.
Supplier Concentrations and Other Inventory Risks	Supplier Concentrations and Other Inventory Risks
	We have arrangements under which substantially all of our manufacturing activity is subcontracted to third-party vendors. Currently we have our manufacturing relationships with Plexus Corp. and Celestica, Inc., who provides us with a wide range of operational and manufacturing services, including material procurement, final assembly, test quality control, warranty repair, and shipment to our customers and third-party vendors. Contract manufacturing activities are conducted in the United States and are undertaken based on management’s product demand forecasts. Our contract manufacturers procure components necessary to assemble the products anticipated by management’s forecast and test the products according to our quality specifications. If the components are unused for specified periods of time, we may incur carrying charges or obsolete material charges for components that our contract manufacturers purchased to build products to meet our product demand forecasts. Our communications modules and other hardware products consist of commodity parts and certain custom components. Our components are generally available from multiple sources or suppliers. However, some components used in our products are purchased from single or limited sources.
	Finished goods are reported as inventory until title transfers to the customer. Consigned finished goods inventory that is maintained at customer locations is also reported as inventory until consumption or acceptance of the product by the customer. We account for consigned inventory on a first-in, first-out basis and record lower of cost or market or obsolete material charges when appropriate.
Concentration of Credit and Customer Risks	Concentration of Credit and Customer Risks
	Our sales are currently concentrated with a small group of customers and third party device manufacturers principally located in the United States and Australia. In evaluating customer concentration risk, we attribute revenue to our customers, including amounts billed to third party device manufacturers for our communications modules.
	The following table summarizes the percentage of revenue related to our customers’ deployments in excess of 10% of total revenue:
		Year Ended December 31,
		2014			2013		2012
	CHED	21	%		—	%	—	%
	Progress	13			—		—
	PG&E	—			39		30
	FPL	—			20		31
	OG&E	—			—		18
	Each of these total revenue percentages includes amounts related to the customers’ deployments that were billed directly to our third party device manufacturers, as well as direct revenue from the customers. We typically extend credit to our customers and third party device manufacturers and do not require collateral or other security in support of accounts receivable. We attempt to mitigate the credit risk in our trade receivables through our credit evaluation process and payment terms. We analyze the need to reserve for potential credit losses and record allowances for doubtful accounts when necessary. To date, we have not had any significant write-offs of uncollectible accounts receivable, and there was no allowance for doubtful accounts as of December 31, 2014 and 2013.
	The following table summarizes the percentage of accounts receivable from customers and third party device manufacturers in excess of 10% of accounts receivable:
		December 31,
		2014			2013
	Commonwealth Edison Company	19	%		10	%
	Virginia Electric and Power Company	13			10
	CPS	11			—
	Landis + Gyr AG	—			11
	Baltimore Gas and Electric Company	—			26
Advertising Costs	Advertising Costs
	We expense advertising costs as incurred. Advertising costs were $2.2 million, $2.2 million, and $2.5 million for each of the years ended December 31, 2014, 2013, and 2012.
Property and Equipment, Net	Property and Equipment, Net
	Property and equipment are stated at cost less accumulated depreciation. Depreciation is calculated using the straight-line method over the following estimated useful lives:
	Software	3 to 7 years
	Computer and network equipment	2 to 5 years
	Machinery and equipment	3 years
	Furniture and fixtures	3 to 7 years
	Leasehold improvements	Lesser of the lease term or the estimated useful lives of the improvements, generally 1 to 10 years
Intangible and Long-Lived Assets	Intangible and Long-Lived Assets
	We evaluate long-lived assets and amortizable intangible assets for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable in accordance with Financial Accounting Standards Board, or FASB, Accounting Standards Codification, or ASC, Topic 360, Property, Plant and Equipment. 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 (i.e., if the sum of its estimated future undiscounted cash flows used to test for recoverability is less than its carrying value), the impairment loss to be recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets. Intangible assets with definite lives are being amortized over the estimated useful lives of the related assets. Each period, we evaluate the estimated remaining useful life of purchased intangible assets and whether events or changes in circumstances warrant a revision to the remaining period of amortization. For the years ended December 31, 2014, 2013, and 2012, no impairment losses were recorded.
Goodwill	Goodwill
	Goodwill represents the excess of the purchase price over the fair value of the net tangible and identifiable intangible assets acquired in a business combination. Goodwill is not subject to amortization but is subject to annual assessment, at a minimum, for impairment in accordance with ASC Topic 350, Intangibles — Goodwill and Other. We evaluate goodwill, at a minimum, on an annual basis and whenever events and changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Impairment of goodwill is tested at the reporting unit level. We first assesses qualitative factors to determine whether the existence of events or circumstances leads to a determination that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If, after assessing the totality of events or circumstances, it is determined it is more likely than not that the fair value of a reporting unit is less than its carrying amount, then we perform the two-step impairment test to measure the amount of the impairment loss, if any. For the years ended December 31, 2014, 2013, and 2012, no impairment losses were recorded.
Research and Development	Research and Development
	Research and development costs are expensed as incurred. Under our current practice of developing new products, technological feasibility of the underlying software is not established until substantially all product development and testing is complete, which generally includes the development of a working model. Our products are released within a short period of time after achieving technological feasibility.
Corporate Bonus Incentive Plan	Corporate Bonus Incentive Plan
	Our corporate bonus incentive plan is funded by a combination of cash and restricted stock units, at management’s discretion. We accrue and record the related corporate bonus amounts payable, both in cash and restricted stock units, under this plan in the period in which it is earned. The Compensation Committee may make incentive awards based on such terms, conditions and criteria as it considers appropriate. Stock awards issued in connection with this plan are generally fully vested at the time of grant. Because the award of share-based payments described above represents an obligation to issue a variable number of the Company’s shares determined on the basis of a monetary value derived solely on variations in an operating performance measure (and not on the basis of variations in the fair value of the entity’s equity shares), the award is considered a share-based liability in accordance with ASC Topic 480, Distinguishing Liabilities from Equity (“ASC 480”) and is remeasured to fair value each reporting period.
Stock-Based Compensation	Stock-Based Compensation
	We measure and recognize compensation expense for all stock-based awards made to employees and directors, including stock options, restricted stock, restricted stock units, and employee stock purchase plan, based on estimated fair values. The fair values of stock options and our 2012 Employee Stock Purchase Plan (please refer to Note 9. Stock Based Compensation for further discussion) are estimated at the date of grant using the Black-Scholes-Merton option pricing model, which includes assumptions for the dividend yield, expected volatility, risk-free interest rate, and expected life. The fair values of restricted stock and restricted stock units are determined based upon the fair value of the underlying common stock at the date of grant. We expense stock-based compensation, adjusted for estimated forfeitures, using the straight-line method over the vesting term of the award. Our excess tax benefits cannot be credited to stockholders’ equity until the deduction reduces cash taxes payable; accordingly, we realized $0.1 million in excess tax benefits during fiscal 2014 and no excess tax during fiscal 2013. The amount of capitalized stock-based employee compensation cost as of December 31, 2014 and 2013 was not material.
Income Taxes	Income Taxes
	We account for income taxes in accordance with ASC Topic 740, Income Taxes, which requires the asset and liability approach for financial accounting and reporting of income taxes. Deferred income taxes are recorded 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. The carrying value of net deferred tax assets reflects that we have been unable to generate sufficient taxable income in certain tax jurisdictions. We record a valuation allowance to reduce our deferred tax assets to the amount of future tax benefit that we believe is more likely than not to be realized. The deferred tax assets are still available for us to use in the future to offset taxable income, which would result in the recognition of a tax benefit and a reduction in our effective tax rate. Actual operating results and the underlying amount and category of income in future years could render our current assumptions, judgments and estimates of the realizability of deferred tax assets inaccurate, which could have a material impact on its financial position or results of operations.
	We follow a two-step approach to recognizing and measuring tax benefits associated with uncertain tax positions taken or expected to be taken in a tax return. The first step is to determine if, based on the technical merits, it is more likely than not that the tax position will be sustained upon examination by a taxing authority, including resolution of any related appeals or litigation processes. The second step is to measure the tax benefit as the largest amount that is more than 50% likely to be realized upon ultimate settlement with a taxing authority. We recognize any interest and penalties related to uncertain tax positions in the provision for income taxes line of our consolidated statements of operations. Accrued interest and penalties are included within the related tax liability line in the consolidated balance sheets.
Recent Accounting Pronouncements	Recent Accounting Pronouncements
	In May 2014, the FASB issued guidance related to revenue from contracts with customers, which supersedes the revenue recognition requirements in ASC 605, Revenue Recognition. Under this guidance, revenue is recognized when promised goods or services are transferred to customers in an amount that reflects the consideration that is expected to be received for those goods or services. The new guidance also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract.  The updated standard will replace most existing revenue recognition guidance under GAAP when it becomes effective and permits the use of either the full retrospective or cumulative effect transition method. Early adoption is not permitted. The updated standard will be effective for us in the first quarter of 2017. We have not yet selected a transition method and we are currently evaluating the effect that the updated standard will have on our consolidated financial statements and related disclosures.

Description_of_Business_and_Su2

Description of Business and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2014
Description of Business and Summary of Significant Accounting Policies [Abstract]
Schedule of Percentage of Revenue Related to Customers' Deployments in Excess of Ten Percent of Total Revenue
		Year Ended December 31,
		2014		2013		2012
	CHED	21	%	—	%	—	%
	Progress	13		—		—
	PG&E	—		39		30
	FPL	—		20		31
	OG&E	—		—		18
Schedule of Percentage of Accounts Receivable from Customers and Third Party Device Manufacturers in Excess of Ten Percent of Accounts Receivable
		December 31,
		2014		2013
	Commonwealth Edison Company	19	%	10	%
	Virginia Electric and Power Company	13		10
	CPS	11		—
	Landis + Gyr AG	—		11
	Baltimore Gas and Electric Company	—		26
Property and Equipment Estimated Useful Lives
	Software	3 to 7 years
	Computer and network equipment	2 to 5 years
	Machinery and equipment	3 years
	Furniture and fixtures	3 to 7 years
	Leasehold improvements	Lesser of the lease term or the estimated useful lives of the improvements, generally 1 to 10 years

Net_Loss_Per_Share_Tables

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2014
Net Loss Per Share [Abstract]
Computation of Historical Basic and Diluted Net Loss Per Share
		Year Ended December 31,
		2014			2013		2012
	Net loss	$	-89,170		$	-66,807	$	-89,717
	Deemed dividend to convertible preferred shareholders		—			-105,000		—
	Net loss attributable to common stockholders	$	-89,170		$	-171,807	$	-89,717
	Weighted-average shares used to compute net loss per share, basic and diluted		48,377			37,877		3,670
	Basic and diluted net loss per share attributable to common stockholders	$	-1.84		$	-4.54	$	-24.45
Common Shares Outstanding were Excluded from Computation of Diluted Net Loss Per Share
		Year Ended December 31,
		2014		2013		2012
	Employee equity incentive plans	6,922		7,760		4,847
	Warrants to purchase convertible preferred stock	—		—		386
	Warrants to purchase common stock	—		—		50
	Convertible preferred stock	—		—		22,366
	Total common stock equivalents	6,922		7,760		27,649

Cash_Cash_Equivalents_And_Shor1

Cash, Cash Equivalents, And Short-Term Investments (Tables)	12 Months Ended
	Dec. 31, 2014
Cash, Cash Equivalents, And Short-Term Investments [Abstract]
Cash, Cash Equivalents and Short-Term Investments
		Amortized		Unrealized		Unrealized		Estimated
		Cost		Gains		Losses		Fair Value
	Current assets:
	Cash	$	54,239	$	—	$	—	$	54,239
	Cash equivalents:
	Money market mutual funds		6,218		—		—		6,218
	Total cash and cash equivalents		60,457		—		—		60,457
	Short-term fixed income securities:
	U.S. government and agency obligations		38,718		46		-18		38,746
	U.S. and foreign corporate debt securities		19,625		9		-33		19,601
	Foreign governments and multi-national agency obligations		2,000		—		-8		1,992
	Total short-term investments		60,343		55		-59		60,339
	Total cash, cash equivalents and short-term investments	$	120,800	$	55	$	-59	$	120,796
	Cash, cash equivalents, and short-term investments consisted of the following as of December 31, 2013 (in thousands):
		Amortized		Unrealized		Unrealized		Estimated
		Cost		Gains		Losses		Fair Value
	Current assets:
	Cash	$	52,346	$	—	$	—	$	52,346
	Cash equivalents:
	Money market mutual funds		30,250		—		—		30,250
	Total cash and cash equivalents		82,596		—		—		82,596
	Short-term fixed income securities:
	U.S. government and agency obligations		41,991		84		-21		42,054
	U.S. and foreign corporate debt securities		18,366		76		-1		18,441
	Foreign governments and multi-national agency obligations		2,764		—		-3		2,761
	Total short-term investments		63,121		160		-25		63,256
	Total cash, cash equivalents and short-term investments	$	145,717	$	160	$	-25	$	145,852
Contractual Maturities of Cash Equivalents and Short-Term Investments
		31-Dec-14				31-Dec-13
		Amortized		Aggregate		Amortized		Aggregate
		Cost Basis		Fair Value		Cost Basis		Fair Value
	Due within one year	$	20,588	$	20,599	$	44,477	$	44,474
	Due after 1 year through 3 years		45,973		45,958		48,894		49,032
	Total cash equivalents and short-term investments	$	66,561	$	66,557	$	93,371	$	93,506
Schedule of Gross Unrealized Losses and Fair Values of Investments
		As of December 31, 2014				As of December 31, 2013
		Total (Less Than 12 Months)				Total (Less Than 12 Months)
		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
	U.S. and foreign corporate debt securities	$	14,563	$	-33	$	4,247	$	-1
	Foreign governments and multi-national agency obligations		1,992		-8		2,761		-3
	U.S. government and agency obligations		13,523		-18		12,566		-21
	Total	$	30,078	$	-59	$	19,574	$	-25

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2014
Fair Value Measurements [Abstract]
Fair Value of Financial Assets Recorded on Recurring Basis
		Fair Value Measurement Using
		Quoted Prices in		Significant
		Active Markets for		Other		Significant
		Identical		Observable		Unobservable
		Instruments		Inputs		Inputs
		(Level 1)		(Level 2)		(Level 3)		Total
	Cash equivalents:
	Money-market funds	$	6,218	$	—	$	—	$	6,218
	Total cash equivalents		6,218		—		—		6,218
	Short-term investments:
	U.S. Government and agency obligations		—		38,746		—		38,746
	U.S. and foreign corporate debt securities		—		19,601		—		19,601
	Foreign governments and multi-national agency obligations		—		1,992		—		1,992
	Total short-term investments		—		60,339		—		60,339
	Total assets measured at fair value	$	6,218	$	60,339	$	—	$	66,557
	As of December 31, 2013, financial assets recorded at fair value on a recurring basis were determined using the following inputs (in thousands):
		Fair Value Measurement Using
		Quoted Prices in		Significant
		Active Markets for		Other		Significant
		Identical		Observable		Unobservable
		Instruments		Inputs		Inputs
		(Level 1)		(Level 2)		(Level 3)		Total
	Cash equivalents:
	Money-market funds	$	30,250	$	—	$	—	$	30,250
	Total cash equivalents		30,250		—		—		30,250
	Short-term investments:
	U.S. Government and agency obligations		—		42,054		—		42,054
	U.S. and foreign corporate debt securities		—		18,441		—		18,441
	Foreign governments and multi-national agency obligations		—		2,761		—		2,761
	Total short-term investments		—		63,256		—		63,256
	Total assets measured at fair value	$	30,250	$	63,256	$	—	$	93,506

Business_Acquisition_Tables

Business Acquisition (Tables)	12 Months Ended
	Dec. 31, 2014
Business Acquisition [Abstract]
Schedule of Business Acquisition
	Cash consideration	$	8,749
	Less: Fair value of net identifiable assets acquired		-4,064
	Goodwill	$	4,685
Assets Acquired And Liabilities Assumed
	Net tangible assets, excluding deferred revenue	$	621
	Deferred revenue		-350
	Intangible assets subject to amortization:
	Developed technology		1,600
	Customer relationships		2,100
	Trade name		300
	In-process research and development (IPR&D)		300
	Deferred tax liabilities in connection with acquired intangible
	assets and other fair value adjustments, net		-507
	Total fair value of net identifiable assets acquired	$	4,064
Amounts Of Revenues And Earnings Included In Statement Of Operations
	Revenues	$	900
	Net loss	$	-509

Goodwill_And_Intangible_Assets1

Goodwill And Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2014
Goodwill And Intangible Assets [Abstract]
Schedule of Goodwill
			December 31,
				2014			2013
	Balance, beginning of period		$	447		$	447
	Goodwill acquired during the period			4,685			-
	Goodwill measurement period adjustment			85			-
	Currency translation adjustment			-488			-
	Balance, end of period		$	4,729		$	447
Schedule Of Intangible Assets	The following table summarizes the gross carrying amount and accumulated amortization for the intangible assets resulting from acquisitions:
		Developed Technology			Customer Relationships			Trade Name		In-process R&D		Total
	Amortization Period	4-5 years			2-7 years			6 years		Indefinite
	Cost:
	Balance at December 31, 2012	$	962		$	260		$	—	$	—	$	1,222
	Balance at December 31, 2013	$	962		$	260		$	—	$	—	$	1,222
	Acquired as a part of SLV acquisition		1,600			2,100			300		300		4,300
	Currency translation adjustment		-166			-220			-31		-31		-448
	Balance at December 31, 2014	$	2,396		$	2,140		$	269	$	269	$	5,074
	Accumulated Amortization:
	Balance at December 31, 2012	$	546		$	260		$	—	$	—	$	806
	Amortization expense		192			—			—		—		192
	Balance at December 31, 2013	$	738		$	260		$	—	$	—	$	998
	Amortization expense		417			169			28		—		614
	Currency translation adjustment		-16			-12			-2		—		-30
	Balance at December 31, 2014	$	1,139		$	417		$	26	$	—	$	1,582
	Intangible assets, net at December 31, 2014	$	1,257		$	1,723		$	243	$	269	$	3,492
	Intangible assets, net at December 31, 2013	$	224		$	—		$	—	$	—	$	224
Schedule Of Amortization Expense
		Year Ended
		December 31,
		2014
	Cost of revenue	$	417
	Selling and marketing		197
	Total	$	614
Schedule Of Estimated Future Amortization Expense
			Year Ended
	2015		$	704
	2016			672
	2017			672
	2018			463
	2019			313
	2020 and thereafter			399
			$	3,223

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2014
Stock-Based Compensation [Abstract]
Stock-Based Compensation Expense
		Year Ended December 31,
		2014			2013			2012
	Cost of revenue	$	7,610		$	12,275		$	2,553
	Research and development		9,677			17,333			4,229
	Sales and marketing		6,062			7,060			2,822
	General and administrative		10,512			15,836			5,488
	Stock-based compensation expense	$	33,861		$	52,504		$	15,092
Summary of Stock Option Activity
		Options Outstanding
				Weighted			Weighted
				Average			Average
				Exercise			Remaining		Aggregate
		Number of		Price per			Contractual		Intrinsic
		Shares		Share			Term (years)		Value
	Balance at December 31, 2013	4,726		$	11.88
	Options granted	732			14.67
	Options exercised	-378			2.94
	Options cancelled or expired	-555			17.57
	Balance at December 31, 2014	4,525		$	12.38		5.67		$	8,699
	As of December 31, 2014:
	Options vested and expected to vest	4,454		$	12.32		5.62		$	8,699
	Options exercisable	3,372		$	11.08		4.65		$	8,699
Summary of Restricted Stock Unit Activity
		Restricted Stock
		Units Outstanding
				Weighted
				Average Grant
		Number of		Date Fair Value
		Shares		per Share
	Balance at December 31, 2013	2,757		$	19.14
	Restricted stock units granted	1,218			10.72
	Restricted stock units vested	-1,280			18.77
	Restricted stock units cancelled	-497			17.50
	Balance at December 31, 2014	2,198		$	15.06
Summary of Assumptions Relating to Stock Options
		Year Ended December 31,
		2014				2013				2012
	Expected volatility		43% - 47	%			47% – 52	%			53.0	%
	Expected dividends		—	%			—	%			—	%
	Expected life in years		6.08				5.00 – 6.08				5.95 – 6.08
	Risk-free interest rate		1.81% - 1.98	%			0.87% – 1.96	%			1.0	%
	Weighted average grant date fair value per share	$	6.60			$	19.11			$	21.20
Summary of Assumptions Relating to ESPP
	Expected volatility	33 - 36	%
	Expected dividends	—	%
	Expected life in years	< 1 year
	Risk-free interest rate	0.05 - 0.08	%

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Taxes [Abstract]
Schedule Of Components Of Loss Before Income Taxes
		Year Ended December 31,
		2014			2013			2012
	United States	$	-57,125		$	-28,774		$	-73,662
	Foreign		-30,623			-37,809			-15,665
	Loss before income taxes	$	-87,748		$	-66,583		$	-89,327
Schedule Of Provision (Benefit) For Income Taxes
		Year Ended December 31,
		2014			2013			2012
	Current:
	United States federal	$	—		$	—		$	—
	State		1,191			-115			382
	Foreign		613			452			306
	Total current provision for income taxes		1,804			337			688
	Deferred:
	United States federal		—			-47			—
	State		—			123			—
	Foreign		-382			-189			-298
	Total deferred benefit for income taxes		-382			-113			-298
	Provision for income taxes	$	1,422		$	224		$	390
Reconciliation Of Federal Statutory Income Tax Rate To Effective Income Tax Rate
		Year Ended December 31,
		2014			2013			2012
	Federal statutory tax expense (benefit)	$	-30,031		$	-23,304		$	-31,265
	Research tax credit		-574			-884			—
	Effect of non-U.S. operations		10,754			13,320			5,469
	Change in valuation allowance		18,166			-925			23,732
	Stock-based compensation expense		1,982			3,455			2,665
	Remeasurement of preferred stock warrant liability		—			—			-752
	Loss on debt extinguishments		—			8,287			—
	Other		1,125			275			541
	Provision for income taxes	$	1,422		$	224		$	390
Schedule Of Components Of Deferred Tax Assets And Liabilities
		December 31,
		2014			2013
	Deferred tax assets:
	Net operating loss and tax credit carryforwards	$	129,471		$	157,971
	Deferred revenue		159,523			96,054
	Stock-based compensation expense		12,241			11,415
	Warrant liability		—			—
	Accruals and reserves		7,452			5,793
	Intangible assets		1,434			1,480
	Other		355			343
	Gross deferred tax assets		310,476			273,056
	Valuation allowance		-186,273			-168,092
	Deferred tax assets		124,203			104,964
	Deferred tax liabilities
	Property and equipment, net		-1,612			-1,905
	Deferred cost of revenue		-122,116			-102,459
	Deferred tax liabilities		-123,728			-104,364
	Net deferred tax assets	$	475		$	600
Summary Of Deferred Tax Assets Valuation Allowance
					Balance at Beginning of Period			Net Change			Balance at End of Period
	Deferred tax assets valuation allowances
		Year ended December 31, 2012		$	141,820		$	25,175		$	166,995
		Year ended December 31, 2013			166,995			1,097			168,092
		Year ended December 31, 2014			168,092			18,181			186,273
Reconciliation Of Beginning And Ending Amounts Of Unrecognized Tax Benefits
		Year Ended December 31,
		2014			2013			2012
	Unrecognized tax benefits—beginning of period	$	8,715		$	5,586		$	4,393
	Gross increase for tax positions of prior years		165			1,216			774
	Gross decrease for tax positions of prior years		-13			—			—
	Gross increase for tax positions of current year		1,778			1,913			419
	Unrecognized tax benefits balance—end of period	$	10,645		$	8,715		$	5,586

Segment_Information_Tables

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2014
Segment Information [Abstract]
Schedule Of Revenue By Geographic Region
		Year Ended December 31,
		2014		2013		2012
	Revenue:
	United States	$	101,579	$	285,430	$	181,948
	Australia		62,745		40,939		13,905
	All Other		26,964		489		884
	Total	$	191,288	$	326,858	$	196,737

Balance_Sheet_Details_Tables

Balance Sheet Details (Tables)	12 Months Ended
	Dec. 31, 2014
Balance Sheet Details [Abstract]
Schedule Of Deferred Revenue
		Year Ended December 31,
		2014			2013
	Deferred revenue, beginning of period	$	524,653		$	508,056
	Revenue deferred in the period		276,228			343,455
	Revenue recognized in the period		-191,288			-326,858
	Deferred revenue, end of period	$	609,593		$	524,653
	Deferred revenue, current		91,688	—	—	111,293
	Deferred revenue, non-current		517,905	—	—	413,360
	Deferred revenue, end of period	$	609,593		$	524,653
Schedule Of Deferred Cost Of Revenue
		Year Ended December 31,
		2014			2013
	Deferred cost of revenue, beginning of period	$	276,123		$	245,163
	Costs deferred related to revenue deferred in the period		123,001			170,213
	Cost of revenue recognized in the period		-66,094			-139,253
	Deferred cost of revenue, end of period	$	333,030		$	276,123
	Deferred cost of revenue, current		29,585	—	—	37,460
	Deferred cost of revenue, non-current		303,445	—	—	238,663
	Deferred cost of revenue, end of period	$	333,030		$	276,123
Components Of Inventory
		December 31,
		2014			2013
	Component parts	$	2,843		$	141
	Finished goods		3,879			4,209
	Inventory	$	6,722		$	4,350
Schedule Of Property And Equipment
		December 31,
		2014			2013
	Computer and network equipment	$	14,708		$	15,328
	Software		13,460			13,003
	Machinery and equipment		10,538			8,543
	Furniture and fixtures		1,335			929
	Leasehold improvements		2,565			1,161
	Total property and equipment		42,606			38,964
	Less: Accumulated depreciation and amortization		-29,746			-26,600
	Property and equipment, net	$	12,860		$	12,364
Schedule Of Accrued Liabilities
		December 31,
		2014			2013
	Accrued payroll and related expenses	$	8,912		$	10,677
	Accrued operating expenses		2,548			3,949
	Warranty obligations, current		3,838			2,985
	Sales, property and income taxes		1,996			1,202
	Other deferred revenue		4,955			1,994
	Other		1,009			475
	Accrued liabilities	$	23,258		$	21,282
Schedule Of Other Liabilities
		December 31,
		2014			2013
	Warranty obligations, non-current	$	3,397		$	3,104
	Other deferred revenue		9,816			9,174
	Other		1,861			1,961
	Other liabilities	$	15,074		$	14,239
Schedule of Product Warranty Obligation
		December 31,
		2014			2013
	Warranty obligation, current—classified in accrued liabilities	$	3,838		$	2,985
	Warranty obligation, non-current—classified in other liabilities		3,397			3,104
		$	7,235		$	6,089
Schedule of Product Warranty Activity
		Year Ended
		December 31,
		2014				2013		2012
	Warranty obligation—beginning of period	$	6,089		$	6,316		$	9,631
	Warranty expense for new warranties issued		669			1,406			1,372
	Utilization of warranty obligation		-2,562			-1,767			-2,671
	Changes in estimates for pre-existing warranties		3,039			134			-2,016
	Warranty obligation—end of period	$	7,235		$	6,089	—	$	6,316
Schedule Of Accumulated Other Comprehensive Income Loss
		Foreign Currency			Unrealized Gains
		Translation			on Available for
		Adjustments			Sale Securities			Total
	Balance as of December 31, 2013	$	46		$	84		$	130
	Other comprehensive income (loss) before reclassification		-770			-11			-781
	Amounts reclassified from AOCI		—			-128			-128
	Other comprehensive income		-770			-139			-909
	Balance as of December 31, 2014	$	-724		$	-55		$	-779

Restructuring_Tables

Restructuring (Tables)	12 Months Ended
	Dec. 31, 2014
Restructuring [Abstract]
Restructuring Reserve Activity
		Year Ended December 31,
		2014
		Severance Costs
	Balance—December 31, 2013	$	—
	Additions during the period		1,888
	Utilization during the period		-1,653
	Balance—December 31, 2014	$	235

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies [Abstract]
Summary of Sale Leaseback Transactions
				Term		Interest	Financed
	Lease Commencement		Lease Termination	(months)		rate	Amount
	March 2012		March 2015	36		7.4		716
	June 2012		June 2015	36		6.7		960
							$	1,676
Future Minimum Commitments under Operating and Capital Leases
		Operating		Capital
		Leases		Leases
	2015	$	5,507	$	1,163
	2016		4,354		112
	2017		614		—
	2018		624		—
	2019		562		—
	2020 and thereafter		1,489		—
	Net minimum lease payments	$	13,150	$	1,275
	Less amount representing interest				-50
	Present value of net minimum capital lease payments			$	1,225

Selected_Quarterly_Financial_D1

Selected Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2014
Selected Quarterly Financial Data [Abstract]
Schedule Of Quarterly Statements Of Operations Data
		Three Months Ended
		December 31,		September 30,		June 30,		March 31,		December 31,		September 30,		June 30,		March 31,
		2014		2014		2014		2014		2013		2013		2013		2013
	Revenue, net	$	77,411	$	28,041	$	41,607	$	44,229	$	97,164	$	72,481	$	103,510	$	53,703
	Cost of revenue		47,233		26,738		28,195		32,785		63,420		49,255		55,260		43,569
	Gross profit		30,178		1,303		13,412		11,444		33,744		23,226		48,250		10,134
	Operating expenses		28,786		38,723		38,084		38,615		33,792		35,341		38,268		49,708
	Operating income (loss)		1,392		-37,420		-24,672		-27,171		-48		-12,115		9,982		-39,574
	Other income (expense), net		68		7		85		-37		138		-54		-184		-24,728
	Income (loss) before income taxes		1,460		-37,413		-24,587		-27,208		90		-12,169		9,798		-64,302
	Provision for income taxes		959		-140		4		599		-268		100		328		64
	Net income (loss)		501		-37,273		-24,591		-27,807		358		-12,269		9,470		-64,366
	Deemed dividend to convertible preferred stockholders		—		—		—		—		—		—		—		-105,000
	Net income (loss) attributable to common stockholders	$	501	$	-37,273	$	-24,591	$	-27,807	$	358	$	-12,269	$	9,470	$	-169,366
	Net income (loss) per share attributable to common stockholders:
	Basic	$	0.01	$	-0.77	$	-0.51	$	-0.58	$	0.01	$	-0.26	$	0.20	$	-16.18
	Diluted	$	0.01	$	-0.77	$	-0.51	$	-0.58	$	0.01	$	-0.26	$	0.19	$	-16.18
	Weighted average shares used to compute net income (loss) per share attributable to common stockholders:
	Basic	$	48,929	$	48,551	$	48,315	$	47,693	$	47,198	$	46,729	$	46,599	$	10,469
	Diluted	$	50,191	$	48,551	$	48,315	$	47,693	$	49,603	$	46,729	$	48,995	$	10,469

Description_of_Business_and_Su3

Description of Business and Summary of Significant Accounting Policies (Narrative) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Deferred revenue, current	$91,688,000	$111,293,000
Non-current revenue	517,905,000	413,360,000
Deferred revenue, non-current	517,905,000	413,360,000
Realized excess tax benefit	100,000	0
Extended product warranty period		15 years
Allowance for doubtful accounts	0	0
Advertising costs	2,200,000	2,200,000	2,500,000
Long-lived assets impairment charges	0	0	0
Impairment losses	0	0
Contingency Provisions [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Revenues	26,200,000	45,800,000
Deferred revenue, current	4,600,000	13,800,000
Non-current revenue	21,600,000	31,900,000
Deferred revenue, non-current	$21,600,000	$31,900,000
Minimum [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Standard warranty period		1 year
Maximum [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Standard warranty period		5 years

Description_of_Business_and_Su4

Description of Business and Summary of Significant Accounting Policies (Schedule of Percentage of Revenue Related to Customers' Deployments in Excess of Ten Percent of Total Revenue) (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
CHED [Member]
Concentration Risk [Line Items]
Percentage of revenue	21.00%
Progress Energy [Member]
Concentration Risk [Line Items]
Percentage of revenue	13.00%
Pacific Gas and Electric Company [Member]
Concentration Risk [Line Items]
Percentage of revenue		39.00%	30.00%
FPL [Member]
Concentration Risk [Line Items]
Percentage of revenue		20.00%	31.00%
Oklahoma Gas and Electric Company [Member]
Concentration Risk [Line Items]
Percentage of revenue			18.00%

Description_of_Business_and_Su5

Description of Business and Summary of Significant Accounting Policies (Schedule of Percentage of Accounts Receivable from Customers and Third Party Device Manufacturers in Excess of Ten Percent of Accounts Receivable) (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Commonwealth Edison Company [Member]
Concentration Risk [Line Items]
Percentage of accounts receivable in excess of 10% accounts receivable	19.00%	10.00%
Virginia Electric and Power Company [Member]
Concentration Risk [Line Items]
Percentage of accounts receivable in excess of 10% accounts receivable	13.00%	10.00%
CPS Energy [Member]
Concentration Risk [Line Items]
Percentage of accounts receivable in excess of 10% accounts receivable	11.00%
Landis + Gyr AG (acquired by Toshiba Corporation) [Member]
Concentration Risk [Line Items]
Percentage of accounts receivable in excess of 10% accounts receivable		11.00%
Baltimore Gas and Electric Company [Member]
Concentration Risk [Line Items]
Percentage of accounts receivable in excess of 10% accounts receivable		26.00%

Description_of_Business_and_Su6

Description of Business and Summary of Significant Accounting Policies (Property and Equipment Estimated Useful Lives) (Detail)	12 Months Ended
	Dec. 31, 2014
Minimum [Member] | Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment estimated useful lives	3 years
Minimum [Member] | Computer and network equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment estimated useful lives	2 years
Minimum [Member] | Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment estimated useful lives	3 years
Minimum [Member] | Furniture and fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment estimated useful lives	3 years
Minimum [Member] | Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment estimated useful lives	1 year
Maximum [Member] | Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment estimated useful lives	7 years
Maximum [Member] | Computer and network equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment estimated useful lives	5 years
Maximum [Member] | Furniture and fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment estimated useful lives	7 years
Maximum [Member] | Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment estimated useful lives	10 years

Net_Loss_Per_Share_Narrative_D

Net Loss Per Share (Narrative) (Details) (USD $)	3 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2013
Net Loss Per Share [Abstract]
Deemed dividend to convertible preferred stockholders	$105,000	$105,000

Net_Loss_Per_Share_Computation

Net Loss Per Share (Computation of Basic and Diluted Net Loss Per Share) (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net Loss Per Share [Abstract]
Net loss	$501	($37,273)	($24,591)	($27,807)	$358	($12,269)	$9,470	($64,366)	($89,170)	($66,807)	($89,717)
Deemed dividend to convertible preferred shareholders								-105,000		-105,000
Net loss attributable to common stockholders	$501	($37,273)	($24,591)	($27,807)	$358	($12,269)	$9,470	($169,366)	($89,170)	($171,807)	($89,717)
Weighted-average shares used to compute net loss per share, basic and diluted									48,377	37,877	3,670
Basic and diluted net loss per share attributable to common stockholders									($1.84)	($4.54)	($24.45)

Net_Loss_Per_Share_Common_Shar

Net Loss Per Share (Common Shares Outstanding were Excluded from Computation of Diluted Net Loss Per Share) (Details)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total common stock equivalents	6,922	7,760	27,649
Employee equity incentive plans [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total common stock equivalents	6,922	7,760	4,847
Warrants to purchase convertible preferred stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total common stock equivalents			386
Warrants to purchase common stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total common stock equivalents			50
Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total common stock equivalents			22,366

Cash_Cash_Equivalents_And_Shor2

Cash, Cash Equivalents, And Short-Term Investments (Narrative) (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
	item	item
Cash and Cash Equivalents [Line Items]
Number of financial institutions	2	3
Financial institution One [Member]
Cash and Cash Equivalents [Line Items]
Percentage of cash and cash equivalents held in financial institutions	46.00%	41.00%
Financial institution Two [Member]
Cash and Cash Equivalents [Line Items]
Percentage of cash and cash equivalents held in financial institutions	42.00%	34.00%
Financial Institution Three [Member]
Cash and Cash Equivalents [Line Items]
Percentage of cash and cash equivalents held in financial institutions		21.00%

Cash_Cash_Equivalents_And_Shor3

Cash, Cash Equivalents, And Short-Term Investments (Cash, Cash Equivalents and Short-Term Investments) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$120,800	$145,717
Unrealized Gains	55	160
Unrealized Losses	-59	-25
Estimated Fair Value	120,796	145,852
Cash [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	54,239	52,346
Estimated Fair Value	54,239	52,346
Cash equivalents [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	60,457	82,596
Estimated Fair Value	60,457	82,596
Cash equivalents [Member] | Money market mutual funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	6,218	30,250
Estimated Fair Value	6,218	30,250
Short-term investments [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	60,343	63,121
Unrealized Gains	55	160
Unrealized Losses	-59	-25
Estimated Fair Value	60,339	63,256
Short-term investments [Member] | U.S. Government and agency obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	38,718	41,991
Unrealized Gains	46	84
Unrealized Losses	-18	-21
Estimated Fair Value	38,746	42,054
Short-term investments [Member] | U.S. and foreign corporate debt securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	19,625	18,366
Unrealized Gains	9	76
Unrealized Losses	-33	-1
Estimated Fair Value	19,601	18,441
Short-term investments [Member] | Foreign governments and multi-national agency obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	2,000	2,764
Unrealized Losses	-8	-3
Estimated Fair Value	$1,992	$2,761

Cash_Cash_Equivalents_And_Shor4

Cash, Cash Equivalents, And Short-Term Investments (Contractual Maturities of Cash Equivalents and Short-Term Investments) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Cash, Cash Equivalents, And Short-Term Investments [Abstract]
Due within one year, Amortized Cost Basis	$20,588	$44,477
Due after 1 year through 3 years, Amortized Cost Basis	45,973	48,894
Total cash equivalents & short-term investments, Amortized Cost Basis	66,561	93,371
Due within one year, Aggregate Fair Value	20,599	44,474
Due after 1 year through 3 years, Aggregate Fair Value	45,958	49,032
Total cash equivalents & short-term investments, Aggregate Fair Value	$66,557	$93,506

Cash_Cash_Equivalents_And_Shor5

Cash, Cash Equivalents, And Short-Term Investments (Schedule of Gross Unrealized Losses and Fair Values of Investments) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Fair Value Total (Less Than 12 Months)	$30,078,000	$19,574,000
Unrealized Loss Total (Less Than 12 Months)	-59,000	-25,000
Unrealized Loss Total (12 months or more)	0	0
U.S. and foreign corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value Total (Less Than 12 Months)	14,563,000	4,247,000
Unrealized Loss Total (Less Than 12 Months)	-33,000	-1,000
Foreign governments and multi-national agency obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value Total (Less Than 12 Months)	1,992,000	2,761,000
Unrealized Loss Total (Less Than 12 Months)	-8,000	-3,000
U.S. Government and agency obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value Total (Less Than 12 Months)	13,523,000	12,566,000
Unrealized Loss Total (Less Than 12 Months)	($18,000)	($21,000)

Fair_Value_Measurements_Fair_V

Fair Value Measurements (Fair Value of Financial Assets Recorded on Recurring Basis) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liabilities recorded at fair value on recurring basis	$0	$0
Assets recorded at fair value, nonrecurring	0	0
Liabilities recorded at fair value, nonrecurring	0	0
Fair value on a recurring basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	66,557,000	93,506,000
Fair value on a recurring basis [Member] | Cash equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	6,218,000	30,250,000
Fair value on a recurring basis [Member] | Cash equivalents [Member] | Money market mutual funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	6,218,000	30,250,000
Fair value on a recurring basis [Member] | Short-term investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	60,339,000	63,256,000
Fair value on a recurring basis [Member] | Short-term investments [Member] | U.S. Government and agency obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	38,746,000	42,054,000
Fair value on a recurring basis [Member] | Short-term investments [Member] | U.S. and foreign corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	19,601,000	18,441,000
Fair value on a recurring basis [Member] | Short-term investments [Member] | Foreign governments and multi-national agency obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	1,992,000	2,761,000
Fair value on a recurring basis [Member] | Quoted Prices in Active Markets for Identical Instruments (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	6,218,000	30,250,000
Fair value on a recurring basis [Member] | Quoted Prices in Active Markets for Identical Instruments (Level 1) [Member] | Cash equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	6,218,000	30,250,000
Fair value on a recurring basis [Member] | Quoted Prices in Active Markets for Identical Instruments (Level 1) [Member] | Cash equivalents [Member] | Money market mutual funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	6,218,000	30,250,000
Fair value on a recurring basis [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	60,339,000	63,256,000
Fair value on a recurring basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Short-term investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	60,339,000	63,256,000
Fair value on a recurring basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Short-term investments [Member] | U.S. Government and agency obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	38,746,000	42,054,000
Fair value on a recurring basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Short-term investments [Member] | U.S. and foreign corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	19,601,000	18,441,000
Fair value on a recurring basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Short-term investments [Member] | Foreign governments and multi-national agency obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	$1,992,000	$2,761,000

Business_Acquisition_Narrative

Business Acquisition (Narrative) (Details)

12 Months Ended

0 Months Ended

1 Months Ended

3 Months Ended

12 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

0 Months Ended

12 Months Ended

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

23-May-14

23-May-14

23-May-14

Dec. 31, 2014

Dec. 31, 2014

6-May-14

Dec. 31, 2014

Dec. 31, 2013

23-May-14

Dec. 31, 2014

Dec. 31, 2014

23-May-14

Dec. 31, 2014

Dec. 31, 2014

23-May-14

Dec. 31, 2014

23-May-14

Dec. 31, 2014

Dec. 31, 2014

Dec. 31, 2014

Dec. 31, 2014

Dec. 31, 2014

Dec. 31, 2014

Dec. 31, 2014

USD ($)

USD ($)

USD ($)

StreetLight Vision [Member]

StreetLight Vision [Member]

StreetLight Vision [Member]

StreetLight Vision [Member]

StreetLight Vision [Member]

StreetLight Vision [Member]

Developed technology [Member]

Developed technology [Member]

Developed technology [Member]

Developed technology [Member]

Customer relationships [Member]

Customer relationships [Member]

Customer relationships [Member]

Trade Names [Member]

Trade Names [Member]

Trade Names [Member]

In Process Research and Development [Member]

In Process Research and Development [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

USD ($)

USD ($)

EUR (€)

USD ($)

USD ($)

USD ($)

USD ($)

StreetLight Vision [Member]

StreetLight Vision [Member]

USD ($)

StreetLight Vision [Member]

StreetLight Vision [Member]

USD ($)

StreetLight Vision [Member]

StreetLight Vision [Member]

StreetLight Vision [Member]

StreetLight Vision [Member]

StreetLight Vision [Member]

Developed technology [Member]

Customer relationships [Member]

StreetLight Vision [Member]

Developed technology [Member]

Customer relationships [Member]

USD ($)

USD ($)

USD ($)

USD ($)

Business Acquisition [Line Items]

Purchase agreements percent of shares acquired

100.00%

Business acquisition cash price

$8,749,000

Escrow deposit

2,600,000

Escrow deposit threshold

1,300,000

Escrow deposit threshold period

12 months

12 months

Escrow deposit conclusion period

24 months

24 months

Remaining payment

1,300,000

Outstanding debt

1,600,000

1,200,000

Increase (decrease) in net assets acquired

-100,000

Intangible assets

4,300,000

1,600,000

2,100,000

300,000

300,000

Discount rate

17.00%

19.00%

19.00%

20.00%

Amortization expenses for intangible assets

614,000

192,000

4,000,000

417,000

192,000

169,000

28,000

Intangible assets, useful life

6 years

4 years

4 years

2 years

7 years

5 years

7 years

Goodwill

4,729,000

447,000

447,000

4,700,000

4,685,000

4,685,000

Acquisition related costs

$400,000

$400,000

Business_Acquisition_Schedule_

Business Acquisition (Schedule of Business Acquisition) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	23-May-14
Business Acquisition [Line Items]
Goodwill	$4,729	$447	$447
StreetLight Vision [Member]
Business Acquisition [Line Items]
Cash consideration	8,749
Less: Fair value of net identifiable assets acquired	-4,064
Goodwill	$4,685			$4,700

Business_Acquisition_Assets_Ac

Business Acquisition (Assets Acquired And Liabilities Assumed) (Details) (StreetLight Vision [Member], USD $)	Dec. 31, 2014	23-May-14
In Thousands, unless otherwise specified
Business Acquisition [Line Items]
Net tangible assets, excluding deferred revenue	$621
Deferred revenue	-350
Intangible assets subject to amortization		4,300
Deferred tax liabilities in connection with acquired intangible assets and other fair value adjustments, net	-507
Total Fair value of net identifiable assets acquired	4,064
Developed technology [Member]
Business Acquisition [Line Items]
Intangible assets subject to amortization	1,600
Customer relationships [Member]
Business Acquisition [Line Items]
Intangible assets subject to amortization	2,100
Trade Names [Member]
Business Acquisition [Line Items]
Intangible assets subject to amortization	300
In Process Research and Development [Member]
Business Acquisition [Line Items]
Intangible assets subject to amortization	$300

Business_Acquisition_Amounts_O

Business Acquisition (Amounts Of Revenues And Earnings Included In Statement Of Operations) (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Business Acquisition [Line Items]
Net loss	$501	($37,273)	($24,591)	($27,807)	$358	($12,269)	$9,470	($64,366)	($89,170)	($66,807)	($89,717)
StreetLight Vision [Member]
Business Acquisition [Line Items]
Revenues									900
Net loss									($509)

Goodwill_And_Intangible_Assets2

Goodwill And Intangible Assets (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	23-May-14
Business Acquisition [Line Items]
Goodwill	$4,729,000	$447,000	$447,000
StreetLight Vision [Member]
Business Acquisition [Line Items]
Goodwill	4,685,000			4,700,000
Increase (decrease) in goodwill	100,000
Intangible assets				$4,300,000

Goodwill_And_Intangible_Assets3

Goodwill And Intangible Assets (Schedule Of Goodwill) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2012
Balance Sheet Details [Abstract]
Balance, beginning of period	$447	$447
Goodwill acquired during the period	4,685
Goodwill measurement period adjustment	85
Currency translation adjustment	-488
Goodwill	$4,729	$447

Goodwill_And_Intangible_Assets4

Goodwill And Intangible Assets (Schedule Of Intangible Assets) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule Of Intangible Assets [Line Items]
Cost, Beginning balance	$1,222	$1,222
Acquired as a part of SLV acquisition	4,300
Currency translation adjustment	-448
Cost, Ending balance	5,074	1,222
Accumulated amortization, beginning balance	998	806
Amortization expense	614	192
Currency translation adjustment	-30
Accumulated amortization, ending balance	1,582	998
Intangible assets, net	3,492	224
In Process Research and Development [Member]
Schedule Of Intangible Assets [Line Items]
Indefinite-lived cost, Acquired as a part of SLV acquisition	300
Indefinite-lived cost, Currency translation adjustment	-31
Indefinite-lived cost, ending balance	269
Intangible assets, net	269
Developed technology [Member]
Schedule Of Intangible Assets [Line Items]
Finited-lived cost, beginning balance	962	962
Finite-lived cost, Acquired as a part of SLV acquisition	1,600
Finite-lived cost, Currency translation adjustment	-166
Finited-lived cost, beginning balance	2,396	962
Accumulated amortization, beginning balance	738	546
Amortization expense	417	192
Currency translation adjustment	-16
Accumulated amortization, ending balance	1,139	738
Intangible assets, net	1,257	224
Customer relationships [Member]
Schedule Of Intangible Assets [Line Items]
Finited-lived cost, beginning balance	260		260
Finite-lived cost, Acquired as a part of SLV acquisition	2,100
Finite-lived cost, Currency translation adjustment	-220
Finited-lived cost, beginning balance	2,140		260
Accumulated amortization, beginning balance	260		260
Amortization expense	169
Currency translation adjustment	-12
Accumulated amortization, ending balance	417		260
Intangible assets, net	1,723
Trade Names [Member]
Schedule Of Intangible Assets [Line Items]
Amortization Period	6 years
Finite-lived cost, Acquired as a part of SLV acquisition	300
Finite-lived cost, Currency translation adjustment	-31
Finited-lived cost, beginning balance	269
Amortization expense	28
Currency translation adjustment	-2
Accumulated amortization, ending balance	26
Intangible assets, net	$243
Minimum [Member] | Developed technology [Member]
Schedule Of Intangible Assets [Line Items]
Amortization Period	4 years
Minimum [Member] | Customer relationships [Member]
Schedule Of Intangible Assets [Line Items]
Amortization Period	2 years
Maximum [Member] | Developed technology [Member]
Schedule Of Intangible Assets [Line Items]
Amortization Period	5 years
Maximum [Member] | Customer relationships [Member]
Schedule Of Intangible Assets [Line Items]
Amortization Period	7 years

Goodwill_And_Intangible_Assets5

Goodwill And Intangible Assets (Schedule Of Amortization Expense) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$614	$192
Cost of revenue [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization expense	417
Sales and marketing [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$197

Goodwill_And_Intangible_Assets6

Goodwill And Intangible Assets (Schedule Of Estimated Future Amortization Expense) (Details) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Goodwill And Intangible Assets [Abstract]
2015	$704
2016	672
2017	672
2018	463
2019	313
2020 and thereafter	399
Total future estimated amortization expense	$3,223

Recovered_Sheet1

Convertible Preferred Stock and Preferred Stock Warrants (Narrative) (Detail) (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2014
Subsidiary, Sale of Stock [Line Items]
Convertible Preferred Stock, Shares Issued and Outstanding		32,406,995
Outstanding convertible securities converted into common stock	32,406,995
Affiliates ownership on common stock	32.70%
Payments for termination of preferred stock warrants	$12
Loss due to reduction of preferred stock warrant liability	0.8
Proceeds from private placement	12
Common stock shares issued	47,384,000	49,062,000
Series D preferred stock [Member]
Subsidiary, Sale of Stock [Line Items]
Conversion price for preferred stockholders, per share	$38.93
Series E convertible preferred stock [Member]
Subsidiary, Sale of Stock [Line Items]
Conversion price for preferred stockholders, per share	$50
Deemed dividend	105
Dividends Preferred Stock Stock	105
Series A Preferred Stock [Member]
Subsidiary, Sale of Stock [Line Items]
Warrants held to purchase preferred stock shares	41,993
Series C Preferred Stock [Member]
Subsidiary, Sale of Stock [Line Items]
Warrants held to purchase preferred stock shares	333,333
Private placement [Member]
Subsidiary, Sale of Stock [Line Items]
Proceeds from private placement	$12
Common stock shares issued	705,881
Price per share issued under private placement	$17
Price per share under IPO	$17

Common_Stock_Narrative_Details

Common Stock (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2014	Feb. 28, 2012	Dec. 31, 2011	Mar. 12, 2013
Common Stock [Line Items]
Common Stock Shares Issued	47,384,000	49,062,000
Proceeds from initial public offering, net of offering costs	$84,247,000
Outstanding convertible securities converted into common stock	32,406,995
Common stock, shares authorized	1,000,000,000	1,000,000,000
Preferred stock, shares authorized		10,000,000
Reduction in preferred stock warranty	11,200,000
Loss due to reduction of preferred stock warrant liability	800,000
Payments for termination of preferred stock warrants	12,000,000
Subordinated convertible notes [Member]
Common Stock [Line Items]
Convertible promissory note			30,000,000	24,000,000
Convertible Promissory Notes [Member]
Common Stock [Line Items]
Interest Payable	2,300,000
Outstanding convertible securities converted into common stock	3,764,954
Initial public offering [Member]
Common Stock [Line Items]
Common Stock Shares Issued	5,462,500
Share Price	$17
Offering costs	2,200,000
Offering expenses	4,200,000
Underwriting discounts and commisions	6,500,000
Initial public offering [Member] | Subordinated convertible notes [Member]
Common Stock [Line Items]
Interest Payable	$2,300,000
Outstanding convertible securities converted into common stock	3,764,954
Private placement [Member]
Common Stock [Line Items]
Common Stock Shares Issued	705,881
Share Price	$17
2012 Equity Incentive Plan [Member]
Common Stock [Line Items]
Common stock shares reserved for issuance					3,400,000
2012 Employee Stock Purchase Plan [Member]
Common Stock [Line Items]
Common stock shares reserved for issuance	2,500,000	4,300,000
ESPP [Member]
Common Stock [Line Items]
Common stock shares reserved for issuance					400,000
Maximum employees contribution		15.00%
Purchase price of the stock as a percent of price of common stock		85.00%
Stock options [Member]
Common Stock [Line Items]
Vesting period		4 years
Incentive Stock Options with person whom own more than 10% of voting power of all classes of stock [Member] | 2012 Equity Incentive Plan [Member]
Common Stock [Line Items]
Percent of voting power		10.00%
Contractual term		5 years
Purchase price of the stock as a percent of price of common stock		110.00%
All options excluding Incentive Stock Options with person whom own more than 10% of voting power of all classes of stock [Member]
Common Stock [Line Items]
Contractual term		10 years
Minimum [Member] | Restricted stock units [Member]
Common Stock [Line Items]
Vesting period		2 years
Maximum [Member] | Restricted stock units [Member]
Common Stock [Line Items]
Vesting period		4 years

Common_Stock_Common_Stock_Warr

Common Stock (Common Stock Warrants Narrative) (Details) (USD $)	1 Months Ended	12 Months Ended
	Mar. 31, 2011	Dec. 31, 2014	Dec. 31, 2013
Class of Warrant or Right [Line Items]
Common stock issued		49,062,000	47,384,000
Warrant [Member]
Class of Warrant or Right [Line Items]
Purchase of common stock by granted warrant	50,000
Exercise price of common stock warrant	$0.01
Warrant expires on exercisable and non-forfeitable		31-Mar-16
Preferred stock converted in to warrants to purchase common stock			20,768
Weighted average exercise price			13.91
Common stock issued			57,370
Warrants to Purchase Convertible Preferred Stock, Price per Share			13.91

StockBased_Compensation_Narrat

Stock-Based Compensation (Narrative) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$33,861,000	$52,504,000	$15,092,000
Accrued payroll and related expenses	8,912,000	10,677,000
Cash received from the exercise of stock options	1,100,000	2,900,000	600,000
Intrinsic value of stock options exercised	3,600,000	9,500,000	6,600,000
Unrecognized compensation costs	28,500,000
Weighted-average period of recognized stock-based compensation expenses	2 years 6 months
2010 Corporate Bonus Incentive Plan And 2011 Corporate Bonus Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		14,600,000
Corporate Bonus Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	300,000	1,600,000	0
Accrued payroll and related expenses	1,900,000	1,600,000
Restricted stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value on the respective dates of restricted stock units	17,300,000	19,500,000	300,000
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$4,700,000

StockBased_Compensation_StockB

Stock-Based Compensation (Stock-Based Compensation Expense) (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$33,861	$52,504	$15,092
Cost of revenue [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	7,610	12,275	2,553
Research and development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	9,677	17,333	4,229
Sales and marketing [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	6,062	7,060	2,822
General and administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$10,512	$15,836	$5,488

StockBased_Compensation_Summar

Stock-Based Compensation (Summary of Stock Option Activity) (Detail) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014
Stock-Based Compensation [Abstract]
Beginning balance	4,726
Number of Shares, Options granted	732
Number of Shares, Options exercised	-378
Number of Shares, Options cancelled or expired	-555
Ending balance	4,525
Number of Shares, Options vested and expected to vest	4,454
Number of Shares, Options exercisable	3,372
Weighted Average Exercise Price Per Share, Beginning balance	$11.88
Weighted Average Exercise Price Per Share, Options granted	$14.67
Weighted Average Exercise Price Per Share, Options exercised	$2.94
Weighted Average Exercise Price Per Share, Options cancelled or expired	$17.57
Weighted Average Exercise Price Per Share, Ending balance	$12.38
Weighted Average Exercise Price Per Share, Options vested and expected to vest	$12.32
Weighted Average Exercise Price Per Share, Options exercisable	$11.08
Weighted Average Remaining Contractual Term, Ending balance	5 years 8 months 1 day
Weighted Average Remaining Contractual Term, Options vested and expected to vest	5 years 7 months 13 days
Weighted Average Remaining Contractual Term, Options exercisable	4 years 7 months 24 days
Aggregate Intrinsic Value, Ending balance	$8,699
Aggregate Intrinsic Value, Options vested and expected to vest	8,699
Aggregate Intrinsic Value, Option exercisable	$8,699

StockBased_Compensation_Summar1

Stock-Based Compensation (Summary of Restricted Stock Unit Activity) (Detail) (Restricted stock units [Member], USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014
Restricted stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance, Number of Shares	2,757
Restricted stock units granted, Number of Shares	1,218
Restricted stock units vested, Number of Shares	-1,280
Restricted stock units cancelled, Number of Shares	-497
Ending balance, Number of Shares	2,198
Beginning balance, Weighted Average Grant Date Fair Value per Share	$19.14
Restricted stock units granted, Weighted Average Grant Date Fair Value per Share	$10.72
Restricted stock units vested, Weighted Average Grant Date Fair Value per Share	$18.77
Restricted stock units cancelled, Weighted Average Grant Date Fair Value per Share	$17.50
Ending balance, Weighted Average Grant Date Fair Value per Share	$15.06

StockBased_Compensation_Summar2

Stock-Based Compensation (Summary of Assumptions Relating to Stock Options) (Details) (Stock options [Member], USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility, minimum	43.00%	47.00%	53.00%
Expected volatility, maximum	47.00%	52.00%
Expected life in years	6 years 29 days
Risk-free interest rate, minimum	1.81%	0.87%	1.00%
Risk-free interest rate, maximum	1.98%	1.96%
Weighted average grant date fair value per share	$6.60	$19.11	$21.20
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected life in years		5 years	5 years 11 months 12 days
Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected life in years		6 years 29 days	6 years 29 days

StockBased_Compensation_Summar3

Stock-Based Compensation (Summary of Assumptions Relating to ESPP) (Details) (ESPP [Member])	12 Months Ended
	Dec. 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility, minimum	33.00%
Expected volatility, maximum	36.00%
Risk-free interest rate, minimum	0.05%
Risk-free interest rate, maximum	0.08%
Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected life in years	1 year

Income_Taxes_Narrative_Details

Income Taxes (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Taxes [Line Items]
Increase in valuation allowance	$18,181,000	$1,097,000	$25,175,000
Undistributed earnings of foreign subsidiaries	5,600,000
Gross unrecognized tax benefits	10,645,000	8,715,000	5,586,000	4,393,000
Unrecognized tax benefits netted against related deferred tax assets	8,700,000	7,100,000
Long Term Liabilities [Member]
Income Taxes [Line Items]
Gross unrecognized tax benefits	200,000
Federal [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	307,500,000
Research tax credit carryforwards	9,300,000
State [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	315,300,000
Research tax credit carryforwards	$10,900,000

Income_Taxes_Schedule_Of_Compo

Income Taxes (Schedule Of Components of Loss Before Income Taxes) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Abstract]
United States	($57,125)	($28,774)	($73,662)
Foreign	-30,623	-37,809	-15,665
Loss before income taxes	($87,748)	($66,583)	($89,327)

Income_Taxes_Schedule_Of_Provi

Income Taxes (Schedule Of Provision (Benefit) For Income Taxes) (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Abstract]
State, Current									$1,191	($115)	$382
Foreign, Current									613	452	306
Total current provision for income taxes									1,804	337	688
United States federal, Deferred										-47
State, Deferred										123
Foreign, Deferred									-382	-189	-298
Total deferred provision (benefit) for income taxes									-382	-113	-298
Provision for income taxes	$959	($140)	$4	$599	($268)	$100	$328	$64	$1,422	$224	$390

Income_Taxes_Reconciliation_Of

Income Taxes (Reconciliation Of Federal Statutory Income Tax Rate To Effective Income Tax Rate) (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Abstract]
Federal statutory tax expense (benefit)									($30,031)	($23,304)	($31,265)
Research tax credit									-574	-884
Effect of non-U.S. operations									10,754	13,320	5,469
Change in valuation allowance									18,166	-925	23,732
Stock-based compensation expense									1,982	3,455	2,665
Remeasurement of preferred stock warrant liability											-752
Loss on debt extinguishments										8,287
Other									1,125	275	541
Provision for income taxes	$959	($140)	$4	$599	($268)	$100	$328	$64	$1,422	$224	$390

Income_Taxes_Schedule_Of_Compo1

Income Taxes (Schedule Of Components Of Deferred Tax Assets and Liabilities) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
Income Taxes [Abstract]
Net operating loss and tax credit carryforwards	$129,471	$157,971
Deferred revenue	159,523	96,054
Stock-based compensation expense	12,241	11,415
Accruals and reserves	7,452	5,793
Intangible assets	1,434	1,480
Other	355	343
Gross deferred tax assets	310,476	273,056
Valuation allowance	-186,273	-168,092	-166,995	-141,820
Deferred tax assets	124,203	104,964
Property and equipment, net	-1,612	-1,905
Deferred cost of revenue	-122,116	-102,459
Deferred tax liabilities	-123,728	-104,364
Net deferred tax assets	$475	$600

Income_Taxes_Summary_Of_Deferr

Income Taxes (Summary Of Deferred Tax Assets Valuation Allowance) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Abstract]
Balance at Beginning of Period	$168,092	$166,995	$141,820
Net change	18,181	1,097	25,175
Balance at End of Period	$186,273	$168,092	$166,995

Recovered_Sheet2

Income Taxes (Reconciliation of Beginning and Ending Amounts of Unrecognized Tax Benefits) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Abstract]
Unrecognized tax benefits-beginning of period	$8,715	$5,586	$4,393
Gross increase for tax positions of prior years	165	1,216	774
Gross decrease for tax positions of prior years	-13
Gross increase for tax positions of current year	1,778	1,913	419
Unrecognized tax benefits balance-end of period	$10,645	$8,715	$5,586

Segment_Information_Details

Segment Information (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
									segment
Segment Reporting Information [Line Items]
Total revenue, net	$77,411	$28,041	$41,607	$44,229	$97,164	$72,481	$103,510	$53,703	$191,288	$326,858	$196,737
Number of Reportable Segments									1
UNITED STATES
Segment Reporting Information [Line Items]
Total revenue, net									101,579	285,430	181,948
AUSTRALIA
Segment Reporting Information [Line Items]
Total revenue, net									62,745	40,939	13,905
All Other [Member]
Segment Reporting Information [Line Items]
Total revenue, net									$26,964	$489	$884

Balance_Sheet_Details_Narrativ

Balance Sheet Details (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Balance Sheet Details [Line Items]
Finished goods	$3,879,000	$4,209,000
Depreciation and amortization expense	5,900,000	6,500,000	7,100,000
Changes in estimates for pre-existing warranties	3,039,000	134,000	-2,016,000
Extended warranty, other current liabilities	582,000	206,000
Extended warranty, other long-term liabilities	8,800,000	7,100,000
Machinery and equipment [Member]
Balance Sheet Details [Line Items]
Assets held under capital leases	4,800,000	6,300,000
Accumulated amortization for assets held under capital leases	3,500,000	3,800,000
Software [Member]
Balance Sheet Details [Line Items]
Assets held under capital leases	3,500,000	3,000,000
Accumulated amortization for assets held under capital leases	2,900,000	2,200,000
Consigned inventory [Member]
Balance Sheet Details [Line Items]
Finished goods	$3,500,000	$2,800,000

Balance_Sheet_Details_Schedule

Balance Sheet Details (Schedule Of Deferred Revenue) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Balance Sheet Details [Abstract]
Deferred revenue, beginning of period	$524,653	$508,056
Revenue deferred in the period	276,228	343,455
Revenue recognized in the period	-191,288	-326,858
Deferred revenue, current	91,688	111,293
Deferred revenue, non-current	517,905	413,360
Deferred revenue, end of period	$609,593	$524,653

Balance_Sheet_Details_Schedule1

Balance Sheet Details (Schedule Of Deferred Cost Of Revenue) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Balance Sheet Details [Abstract]
Deferred cost of revenue, beginning of period	$276,123	$245,163
Costs deferred related to revenue deferred in the period	123,001	170,213
Cost of revenue recognized in the period	-66,094	-139,253
Deferred cost of revenue, current	29,585	37,460
Deferred cost of revenue, non-current	303,445	238,663
Deferred cost of revenue, end of period	$333,030	$276,123

Balance_Sheet_Details_Componen

Balance Sheet Details (Components Of Inventory) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Balance Sheet Details [Abstract]
Component parts	$2,843	$141
Finished goods	3,879	4,209
Inventory	$6,722	$4,350

Balance_Sheet_Details_Schedule2

Balance Sheet Details (Schedule Of Property And Equipment) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Property, Plant and Equipment [Line Items]
Property and equipment	$42,606	$38,964
Less: Accumulated depreciation and amortization	-29,746	-26,600
Property, Plant and Equipment, Net, Total	12,860	12,364
Computer and network equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	14,708	15,328
Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	13,460	13,003
Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	10,538	8,543
Furniture and fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	1,335	929
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	$2,565	$1,161

Balance_Sheet_Details_Schedule3

Balance Sheet Details (Schedule Of Accrued Liabilities) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Balance Sheet Details [Abstract]
Accrued payroll and related expenses	$8,912	$10,677
Accrued operating expenses	2,548	3,949
Product warranty, current	3,838	2,985
Sales, property and income taxes	1,996	1,202
Other deferred revenue	4,955	1,994
Other	1,009	475
Accrued liabilities	$23,258	$21,282

Balance_Sheet_Details_Schedule4

Balance Sheet Details (Schedule Of Other Liabilities) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Balance Sheet Details [Abstract]
Warranty obligations, non-current	$3,397	$3,104
Other deferred revenue	9,816	9,174
Other	1,861	1,961
Other liabilities	$15,074	$14,239

Balance_Sheet_Details_Schedule5

Balance Sheet Details (Schedule of Warranty Obligation) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
Guarantee Obligations [Line Items]
Warranty obligation	$7,235	$6,089	$6,316	$9,631
Accrued liabilities [Member]
Guarantee Obligations [Line Items]
Warranty obligation	3,838	2,985
Other liabilities [Member]
Guarantee Obligations [Line Items]
Warranty obligation	$3,397	$3,104

Balance_Sheet_Details_Schedule6

Balance Sheet Details (Schedule of Product Warranty Activity) (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Balance Sheet Details [Abstract]
Warranty obligation-beginning of period	$6,089	$6,316	$9,631
Warranty expense for new warranties issued	669	1,406	1,372
Utilization of warranty obligation	-2,562	-1,767	-2,671
Changes in estimates for pre-existing warranties	3,039	134	-2,016
Warranty obligation-end of period	$7,235	$6,089	$6,316

Balance_Sheet_Details_Schedule7

Balance Sheet Details (Schedule Of Accumulated Other Comprehensive Income (Loss)) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance as of December 31, 2013	$130
Other comprehensive income before reclassification	-781
Amounts reclassified from AOCI	-128
Other comprehensive income (loss)	-909	266	-119
Balance as of December 31, 2014	-779	130
Foreign Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance as of December 31, 2013	46
Other comprehensive income before reclassification	-770
Other comprehensive income (loss)	-770
Balance as of December 31, 2014	-724
Unrealized Gains on Available for Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance as of December 31, 2013	84
Other comprehensive income before reclassification	-11
Amounts reclassified from AOCI	-128
Other comprehensive income (loss)	-139
Balance as of December 31, 2014	($55)

Borrowings_Narrative_Detail

Borrowings - (Narrative) (Detail) (USD $)	12 Months Ended	1 Months Ended
	Dec. 31, 2013	Feb. 28, 2012	Dec. 31, 2011	Dec. 31, 2014	8-May-13	Apr. 30, 2013
Debt Instrument [Line Items]
Line of credit facility maximum borrowing capacity					$50,000,000	$40,000,000
Outstanding letters of credit				17,000,000
Additional letters of credit				33,000,000
Credit agreement termination, date	17-May-15
Outstanding convertible securities converted into common stock	32,406,995
Loss on debt extinguishments	22,900,000
Subordinated convertible notes [Member]
Debt Instrument [Line Items]
Debt instrument, face amount		30,000,000	24,000,000
Maturity date		21-Feb-15	6-Dec-14
Percentage of accrued interest, minimum		3.00%	3.00%
Percentage of increase in accrued interest		1.00%	1.00%
Percentage of accrued interest, maximum		6.00%	6.00%
Subordinated convertible notes [Member] | Initial public offering [Member]
Debt Instrument [Line Items]
Percentage of convertible stock	88.00%
Outstanding convertible securities converted into common stock	3,764,954
Price per share issued	$17
Loss on debt extinguishments	22,900,000
EON Patent Litigation [Member]
Debt Instrument [Line Items]
Outstanding letters of credit				$13,000,000

Benefit_Plans_Details

Benefit Plans (Details) (USD $)	12 Months Ended
	Dec. 31, 2014
Benefit Plan [Abstract]
Discretionary profit sharing contributions	$0

Restructuring_Narrative_Detail

Restructuring (Narrative) (Details) (2014 Restructuring Plan [Member], USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014
Restructuring Cost and Reserve [Line Items]
Severance Costs	$1.80
Minimum [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Future charges	1.6
Maximum [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Future charges	$2.10

Restructuring_Restructuring_An

Restructuring (Restructuring And Other Charges) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restructuring [Abstract]
Restructuring	$1,789

Restructuring_Restructuring_Re

Restructuring (Restructuring Reserve Activity) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restructuring Cost and Reserve [Line Items]
Additions	$1,789
2014 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance
Additions	1,888
Payments during the period	-1,653
Ending Balance	$235

Commitments_and_Contingencies_1

Commitments and Contingencies (Narrative) (Detail)

12 Months Ended

1 Months Ended

12 Months Ended

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

8-May-13

Apr. 30, 2013

Dec. 31, 2014

Jun. 30, 2014

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

EON Patent Litigation [Member]

EON Patent Litigation [Member]

Standby letters of credit [Member]

Standby letters of credit [Member]

Standby letters of credit [Member]

Standby letters of credit [Member]

Standby letters of credit [Member]

Standby letters of credit [Member]

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

Australian dollars [Member]

Australian dollars [Member]

Australian dollars [Member]

USD ($)

AUD

AUD

Loss Contingencies [Line Items]

Increase (reduction) of product warranty liability and product cost of revenue

$3,039,000

$134,000

($2,016,000)

Rent expense facility leases

5,300,000

4,900,000

4,000,000

Littigation settlement, amount

13,000,000

18,800,000

Pre-judgement interest

1,500,000

Litigation costs

200,000

Surety Bond

17,600,000

13,000,000

Surety bond percent of additional judgement, percent

20.00%

Outstanding letters of credit

17,000,000

13,000,000

Possible estimated loss

14,700,000

Credit facility with financial institution

50,000,000

40,000,000

17,000,000

17,000,000

9,800,000

500,000

600,000

600,000

Unsecured surety bond

$20,300,000

$15,000,000

Commitments_and_Contingencies_2

Commitments and Contingencies (Summary of Sale Leaseback Transactions) (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014
Sale Leaseback Transaction [Line Items]
Financed Amount	$1,676
Lease Commencement, March 2012 [Member]
Sale Leaseback Transaction [Line Items]
Lease Termination	2015-03
Term (months)	36 months
Interest rate	7.40%
Financed Amount	716
Lease Commencement, June 2012 [Member]
Sale Leaseback Transaction [Line Items]
Lease Termination	2015-06
Term (months)	36 months
Interest rate	6.70%
Financed Amount	$960

Commitments_and_Contingencies_3

Commitments and Contingencies (Future Minimum Commitments Under Operating And Capital Leases) (Detail) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Commitments and Contingencies [Abstract]
Operating leases, 2015	$5,507
Operating leases, 2016	4,354
Operating leases, 2017	614
Operating leases, 2018	624
Operating leases, 2019	562
Operating leases, 2020 and thereafter	1,489
Net minimum operating lease payments	13,150
Capital leases, 2015	1,163
Capital leases, 2016	112
Net minimum capital lease payments	1,275
Less amount representing interest	-50
Present value of net minimum capital lease payments	$1,225

Subsequent_Events_Details

Subsequent Events (Details) (Subsequent Event [Member], Detectent, Inc. [Member], USD $)	0 Months Ended
	Jan. 16, 2015
Subsequent Event [Member] | Detectent, Inc. [Member]
Subsequent Event [Line Items]
Cash consideration	$7,700,000
Deferred consideration	4,000,000
Total consideration	$11,700,000

Selected_Quarterly_Financial_D2

Selected Quarterly Financial Data (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Selected Quarterly Financial Data [Abstract]
Revenue, net	$77,411	$28,041	$41,607	$44,229	$97,164	$72,481	$103,510	$53,703	$191,288	$326,858	$196,737
Cost of revenue	47,233	26,738	28,195	32,785	63,420	49,255	55,260	43,569	134,951	211,504	165,018
Gross profit	30,178	1,303	13,412	11,444	33,744	23,226	48,250	10,134	56,337	115,354	31,719
Operating expenses	28,786	38,723	38,084	38,615	33,792	35,341	38,268	49,708	144,208	157,109	120,363
Operating income (loss)	1,392	-37,420	-24,672	-27,171	-48	-12,115	9,982	-39,574	-87,871	-41,755	-88,644
Other income (expense), net	68	7	85	-37	138	-54	-184	-24,728	123	-24,828	-683
Income (loss) before income taxes	1,460	-37,413	-24,587	-27,208	90	-12,169	9,798	-64,302	-87,748	-66,583	-89,327
Provision for income taxes	959	-140	4	599	-268	100	328	64	1,422	224	390
Net income (loss)	501	-37,273	-24,591	-27,807	358	-12,269	9,470	-64,366	-89,170	-66,807	-89,717
Deemed dividend to convertible preferred shareholders								-105,000		-105,000
Net income (loss) attributable to common stockholders	$501	($37,273)	($24,591)	($27,807)	$358	($12,269)	$9,470	($169,366)	($89,170)	($171,807)	($89,717)
Net income (loss) per share attributable to common stockholders:
Basic	$0.01	($0.77)	($0.51)	($0.58)	$0.01	($0.26)	$0.20	($16.18)
Diluted	$0.01	($0.77)	($0.51)	($0.58)	$0.01	($0.26)	$0.19	($16.18)
Weighted average shares used to compute net income (loss) per share attributable to common stockholders:
Basic	48,929	48,551	48,315	47,693	47,198	46,729	46,599	10,469
Diluted	50,191	48,551	48,315	47,693	49,603	46,729	48,995	10,469