Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Statement [Abstract]
Net revenues	$ 185,245us-gaap_Revenues	$ 335,053us-gaap_Revenues	$ 344,288us-gaap_Revenues
Cost of net revenues	148,198us-gaap_CostOfRevenue	266,759us-gaap_CostOfRevenue	271,845us-gaap_CostOfRevenue
Gross profit	37,047us-gaap_GrossProfit	68,294us-gaap_GrossProfit	72,443us-gaap_GrossProfit
Operating costs and expenses:
Research and development	34,314us-gaap_ResearchAndDevelopmentExpense	48,246us-gaap_ResearchAndDevelopmentExpense	60,422us-gaap_ResearchAndDevelopmentExpense
Sales and marketing	13,792us-gaap_SellingAndMarketingExpense	20,898us-gaap_SellingAndMarketingExpense	27,501us-gaap_SellingAndMarketingExpense
General and administrative	15,402us-gaap_GeneralAndAdministrativeExpense	24,179us-gaap_GeneralAndAdministrativeExpense	22,668us-gaap_GeneralAndAdministrativeExpense
Goodwill and intangible assets impairment	0	0	49,521
Amortization of purchased intangible assets	562us-gaap_AmortizationOfIntangibleAssets	562us-gaap_AmortizationOfIntangibleAssets	1,074us-gaap_AmortizationOfIntangibleAssets
Shareholder litigation loss	790nvtl_ContingentLossForLitigation	14,326nvtl_ContingentLossForLitigation	0nvtl_ContingentLossForLitigation
Restructuring charges	7,760us-gaap_RestructuringCharges	3,304us-gaap_RestructuringCharges	0us-gaap_RestructuringCharges
Total operating costs and expenses	72,620us-gaap_OperatingExpenses	111,515us-gaap_OperatingExpenses	161,186us-gaap_OperatingExpenses
Operating loss	(35,573)us-gaap_OperatingIncomeLoss	(43,221)us-gaap_OperatingIncomeLoss	(88,743)us-gaap_OperatingIncomeLoss
Other income (expense):
Change in fair value of warrant liability	(3,280)us-gaap_FairValueAdjustmentOfWarrants	0us-gaap_FairValueAdjustmentOfWarrants	0us-gaap_FairValueAdjustmentOfWarrants
Interest income (expense), net	(85)	113	291
Other expense, net	(167)us-gaap_OtherNonoperatingIncomeExpense	(222)us-gaap_OtherNonoperatingIncomeExpense	(203)us-gaap_OtherNonoperatingIncomeExpense
Loss before income taxes	(39,105)	(43,330)	(88,655)
Income tax provision	124us-gaap_IncomeTaxExpenseBenefit	83us-gaap_IncomeTaxExpenseBenefit	611us-gaap_IncomeTaxExpenseBenefit
Net loss	(39,229)	(43,413)	(89,266)
Recognition of beneficial conversion feature	(445)	0	0
Net loss	$ (39,674)us-gaap_NetIncomeLoss	$ (43,413)us-gaap_NetIncomeLoss	$ (89,266)us-gaap_NetIncomeLoss
Net loss per share:
Basic and diluted net loss per share (dollars per share)	$ (1.05)us-gaap_EarningsPerShareBasicAndDiluted	$ (1.28)us-gaap_EarningsPerShareBasicAndDiluted	$ (2.72)us-gaap_EarningsPerShareBasicAndDiluted
Weighted average shares used in computation of basic and diluted net loss per share attributable to common shareholders:
Weighted-average common shares outstanding (in shares)	37,959	33,948	32,852

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