Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Net operating losses	$ 78,001	$ 50,154
Accruals and reserves	3,514	7,725
Tax credit carryforward	11,013	8,503
Stock-based compensation	8,280	5,944
Depreciation and amortization	4,381	4,735
Total deferred tax assets	105,189	77,061
Valuation allowance	(104,298)	(75,436)	$ (58,748)	$ (59,806)
Net deferred tax assets	891	1,625
Deferred tax liabilities:
Depreciation and amortization	(2,550)	(3,665)
Net deferred taxes	$ (1,659)	$ (2,040)