Income Taxes - Summary (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Provision for income taxes
Provision for income taxes	$ 0	$ 0	$ 0
Net deferred tax assets, before valuation allowance	284,200,000	202,800,000	174,200,000
Unrecognized tax benefits	2,099,000	2,606,000	0
Research Tax Credit Carryforward
Provision for income taxes
Tax credit carryforward	21,000,000
Federal
Provision for income taxes
Net operating loss carryforwards	894,300,000	700,700,000	618,100,000
Operating loss carryforwards, subject to expiration	347,400,000
State
Provision for income taxes
Net operating loss carryforwards	$ 662,200,000	$ 530,300,000	$ 527,100,000