Income Taxes - Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of the federal statutory tax rate to the Company's effective tax rate
Federal statutory tax rate (as a percent)	21.00%	21.00%	21.00%
State and local income taxes (as a percent)	4.50%	6.00%	26.60%
Research and development credits	(28.00%)
Change in uncertain tax positions (as a percent)	6.90%	0.20%	5.50%
Tax benefit from net operating loss carryback	(10.20%)
Permanent items (as a percent)	5.40%	2.30%	27.90%
State tax rate change effect on deferred balance	1.70%		27.70%
Other tax credits	(0.10%)	(0.10%)	(5.60%)
Tax audit adjustments (as a percent)		0.90%	8.70%
Change in valuation allowance (as a percent)		(22.50%)	9.50%
Other (as a percent)	0.40%	1.90%	(1.70%)
Tax provision (as a percent)	1.60%	9.70%	119.60%