Income Taxes - Effective Income Tax Reconciliation (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
U.S. statutory federal rate	21.00%	21.00%	34.00%
Increase (decrease) resulting from:
State taxes, net of federal benefit	3.70%	7.80%	2.50%
Change in U.S. federal statutory rate	0.00%	0.00%	(102.20%)
Nondeductible expenses	8.00%	(13.50%)	(10.50%)
Effect of foreign tax rate differential	2.30%	(0.50%)	(5.30%)
Uncertain tax positions	4.90%	(3.30%)	(1.60%)
Research and development credit	(24.80%)	15.10%	5.60%
Change in valuation allowance	(12.00%)	(36.40%)	77.10%
Expiration of NOL	4.00%	(1.00%)	(0.20%)
Change in U.S. state statutory rate	4.00%	0.60%	(1.70%)
Other	5.40%	1.40%	0.60%
Effective tax rate	16.50%	(8.80%)	(1.70%)