Income Taxes - Components of Deferred Tax Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Deferred tax assets:
Reserves and accruals	$ 21,048	$ 29,235
Net operating loss carryovers	24,946	27,253
Research and development credit carryovers	26,404	18,391
Deferred stock-based compensation	6,727	7,554
Other tax credits	2,738	2,738
Gross deferred tax assets	81,863us-gaap_DeferredTaxAssetsGross	85,171us-gaap_DeferredTaxAssetsGross
Valuation allowance	(75,199)	(38,644)	(34,347)	(28,354)
Gross deferred tax assets after valuation allowance	6,664us-gaap_DeferredTaxAssetsNet	46,527us-gaap_DeferredTaxAssetsNet
Deferred tax liabilities:
Depreciation and amortization	(2,137)	(3,590)
Intangibles	(2,228)	(6,227)
Other	(589)us-gaap_DeferredTaxLiabilitiesOther	(738)us-gaap_DeferredTaxLiabilitiesOther
Gross deferred tax liabilities	(4,954)us-gaap_DeferredTaxLiabilities	(10,555)us-gaap_DeferredTaxLiabilities
Net deferred tax assets	$ 1,710us-gaap_DeferredTaxAssetsLiabilitiesNet	$ 35,972us-gaap_DeferredTaxAssetsLiabilitiesNet

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Amount before allocation of valuation allowances of deferred tax asset attributable to other deductible tax credit carryforwards not separately disclosed.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible research tax credit carryforwards.

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