Fair Value Measurements and Fair Value of Financial Instruments - Unrealized Gain (Loss) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Amortized Cost Basis	$ 493,796	$ 431,808
Unrealized Gains	0	57
Unrealized Losses	(536)	(2)
Fair Value	493,260	431,863
Money market funds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Amortized Cost Basis	232,813	333,585
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	232,813	333,585
U.S. Treasury securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Amortized Cost Basis	260,983	98,223
Unrealized Gains	0	57
Unrealized Losses	(536)	(2)
Fair Value	$ 260,447	$ 98,278