Income Taxes - Tax Effects of Temporary Differences for Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Net operating losses and credits	$ 61,494	$ 23,338
Fixed assets and intangible assets	55,476	10,625
Accruals and reserves	53,818	49,886
Stock-based compensation	9,494	12,154
Inventory	911	4,345
Other	4,806	3,325
Total deferred tax assets	185,999	103,673
Less: valuation allowance	(181,122)	(99,570)
Deferred tax assets, net of valuation allowance	4,877	4,103
Other	(560)	(369)
Total deferred tax liabilities	(560)	(369)
Net deferred tax assets	$ 4,317	$ 3,734