Income Taxes - Reconciliation of Income Taxes at Statutory Rate (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Tax benefit at federal statutory rate	34.00%	34.00%	34.00%
State tax credit (expense), net of federal benefit	2.20%	1.40%	(1.50%)
Foreign tax expense	(0.70%)	(1.90%)	(3.70%)
Change in valuation allowance	(31.20%)	(28.60%)	(21.10%)
Federal research and development credit	1.30%	2.60%	2.70%
Unrecognized tax benefit	(1.30%)	(1.80%)	(0.70%)
Return to provision reconciliation	1.50%	(1.20%)	(0.00%)
Other, net	(0.60%)	(1.90%)	(1.20%)
Effective tax rate	5.20%	2.60%	8.50%