Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Net operating loss carryforwards	$ 91,701	$ 123,913
Reserves and accruals	3,927	4,281
Depreciation and amortization	5,591	712
Tax credit carryforwards	14,838	12,584
Stock-based compensation	5,994	7,057
Total deferred tax assets	122,051	148,547
Valuation allowance on deferred tax assets	(119,228)	(146,285)
Total deferred tax assets, net of valuation allowance	2,823	2,262
Deferred Tax Liabilities, Gross [Abstract]
Fixed asset and intangibles	(18,912)	(22,000)
Total deferred tax liabilities	(18,912)	(22,000)
Net deferred tax liability	$ (16,089)	$ (19,738)