Fair Value of Financial Instruments - Financial Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Assets:
Short-term investments	$ 551,320	$ 490,967
Total	587,701	643,941
Fair Value, Recurring | Level 1 | U.S. Treasury securities
Assets:
Short-term investments	465,370	330,053
Fair Value, Recurring | Level 1 | Corporate debt securities
Assets:
Short-term investments	85,951	160,914
Money market funds | Fair Value, Recurring | Level 1
Assets:
Cash equivalents and marketable securities	36,380	102,978
U.S. Treasury securities | Fair Value, Recurring | Level 1
Assets:
Cash equivalents and marketable securities	$ 0	$ 49,996