Income Taxes - Reconciliation of Effective Tax Rate (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Tax Disclosure [Abstract]
U.S. federal statutory tax rate	21.00%	21.00%	21.00%	21.00%
State income taxes, net of federal benefit	1.70%	1.00%	1.00%	(0.30%)
Non-U.S. income taxed at different rates	0.70%	(3.50%)	1.00%	0.30%
Reduction in tax benefit related to stock-based awards	(1.10%)	6.50%	(1.80%)	(1.50%)
Non-deductible expenses	0.00%	(9.50%)	(0.30%)	(9.30%)
Research and development credit	0.40%	(3.90%)	0.60%	0.60%
Increase in valuation allowance	(20.70%)	(42.20%)	(17.90%)	(36.00%)
Other	(0.40%)	0.00%	(0.30%)	0.00%
Effective income tax rate	1.60%	(30.60%)	3.30%	(25.20%)