Income Taxes - Provision Difference from Federal Statutory Rate (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Effective tax rate of provision for income taxes difference from federal statutory rate
Federal statutory income tax rate (as a percent)	21.00%	21.00%	21.00%
State taxes, net of federal benefit (as a percent)	1.90%	1.90%	1.20%
Research and development credits (as a percent)	4.30%	6.50%	4.30%
Foreign tax rate difference (as a percent)		(0.90%)	0.70%
Change in valuation allowance (as a percent)	(28.00%)	(34.30%)	(23.80%)
Other (as a percent)	0.80%	3.80%	(2.50%)
Provision (benefit) for income taxes		(2.00%)	0.90%