Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Fair Value of Financial Instruments
Marketable securities, available-for-sale	$ 771,254	$ 958,763
U.S. government agency securities
Fair Value of Financial Instruments
Marketable securities, available-for-sale	200,863	372,671
U.S. Treasury obligations
Fair Value of Financial Instruments
Marketable securities, available-for-sale	570,391	586,092
Recurring
Fair Value of Financial Instruments
Total	818,764	1,058,950
Recurring | U.S. government agency securities
Fair Value of Financial Instruments
Marketable securities, available-for-sale	200,863	372,671
Recurring | U.S. Treasury obligations
Fair Value of Financial Instruments
Marketable securities, available-for-sale	570,391	586,092
Recurring | Money market funds
Fair Value of Financial Instruments
Cash equivalents	47,510	95,198
Recurring | U.S. Treasury obligations
Fair Value of Financial Instruments
Cash equivalents		4,989
Recurring | Active Markets (Level 1)
Fair Value of Financial Instruments
Total	617,901	686,279
Recurring | Active Markets (Level 1) | U.S. Treasury obligations
Fair Value of Financial Instruments
Marketable securities, available-for-sale	570,391	586,092
Recurring | Active Markets (Level 1) | Money market funds
Fair Value of Financial Instruments
Cash equivalents	47,510	95,198
Recurring | Active Markets (Level 1) | U.S. Treasury obligations
Fair Value of Financial Instruments
Cash equivalents		4,989
Recurring | Observable Inputs (Level 2)
Fair Value of Financial Instruments
Total	200,863	372,671
Recurring | Observable Inputs (Level 2) | U.S. government agency securities
Fair Value of Financial Instruments
Marketable securities, available-for-sale	$ 200,863	$ 372,671