Income Taxes - Net Deferred Tax Assets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Deferred tax assets:
Reserves and accruals	$ 1,387	$ 1,345
Deferred revenue	8,429us-gaap_DeferredTaxAssetsDeferredIncome	4,297us-gaap_DeferredTaxAssetsDeferredIncome
Stock-based compensation	5,776	7,042
Net operating loss carryforwards	25,519	20,361
Loss on OCI	380	0
Other	41us-gaap_DeferredTaxAssetsOther	194us-gaap_DeferredTaxAssetsOther
Gross deferred tax assets	41,532us-gaap_DeferredTaxAssetsGross	33,239us-gaap_DeferredTaxAssetsGross
Valuation allowance	(40,488)	(32,656)
Total deferred tax assets	1,044us-gaap_DeferredTaxAssetsNet	583us-gaap_DeferredTaxAssetsNet
Deferred tax liabilities:
Stock-based compensation	(53)	(166)
Depreciation and amortization	(1,757)	(31)
Gain on OCI	0	(3)
Total deferred tax liabilities	(1,810)us-gaap_DeferredIncomeTaxLiabilities	(200)us-gaap_DeferredIncomeTaxLiabilities
Net deferred tax assets	$ (766)us-gaap_DeferredTaxAssetsLiabilitiesNet	$ 383us-gaap_DeferredTaxAssetsLiabilitiesNet

Deferred tax liabilities relating to stock based compensation plans.

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Amount of deferred tax liability attributable to taxable temporary differences.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from deferred income.

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Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards, net of deferred tax liability attributable to taxable temporary differences.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences not separately disclosed.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from unrealized losses in other comprehensive income.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from share-based compensation.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from reserves and accruals.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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Amount of deferred tax liability attributable to taxable temporary differences from unrealized gains in other comprehensive income.

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Amount of deferred tax liability attributable to taxable temporary differences from property, plant, and equipment.

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