Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Net operating losses	$ 72,588	$ 70,005
Credits	5,016	4,671
Deferred revenues	1,025	3,357
Stock-based compensation	3,750	3,460
Reserves and accruals	2,952	2,713
Depreciation	2,516	2,377
Intangible assets	5,536	5,127
Capital losses	933	933
Unrealized gain/loss	277	126
Other assets	110	98
Total deferred tax assets:	94,703	92,867
Deferred tax liabilities:
Other	(103)	(199)
Total deferred tax liabilities:	(103)	(199)
Valuation allowance	(94,663)	(92,762)
Net deferred tax liabilities	$ (63)	$ (94)