Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Net operating loss carryovers	$ 70,739	$ 48,912
Research and development and other tax credits	22,613	15,148
Deferred revenue	735	1,210
Intangibles and property and equipment basis difference	0	2,097
Stock compensation expense	5,664	3,488
Other	4,679	1,129
Total deferred tax assets	104,430	71,984
Total deferred tax liabilities	(799)	(343)
Net deferred tax asset	103,631	71,641
Valuation allowance	(103,631)	(71,641)
Net deferred tax asset	$ 0	$ 0