Fair Value Measurements and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets measured at fair value	$ 530,047	$ 431,863
Fair Value, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Money market funds	444,668	333,585
U.S. Treasury securities	85,379	98,278
Total assets measured at fair value	530,047
Level 1 | Fair Value, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Money market funds	444,668	333,585
U.S. Treasury securities	0	0
Total assets measured at fair value	444,668	333,585
Level 2 | Fair Value, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Money market funds	0	0
U.S. Treasury securities	85,379	98,278
Total assets measured at fair value	85,379	98,278
Level 3 | Fair Value, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Money market funds	0	0
U.S. Treasury securities	0	0
Total assets measured at fair value	$ 0	$ 0