Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Fair Value of Financial Instruments
Marketable securities, available-for-sale	$ 901,210	$ 824,695
U.S. government agency securities
Fair Value of Financial Instruments
Marketable securities, available-for-sale	422,416	497,143
U.S. Treasury obligations
Fair Value of Financial Instruments
Marketable securities, available-for-sale	478,794	327,552
Recurring
Fair Value of Financial Instruments
Total	1,175,832	943,575
Recurring | U.S. government agency securities
Fair Value of Financial Instruments
Marketable securities, available-for-sale	422,416	497,143
Recurring | U.S. Treasury obligations
Fair Value of Financial Instruments
Marketable securities, available-for-sale	478,794	327,552
Recurring | Money market funds
Fair Value of Financial Instruments
Cash equivalents	274,622	118,880
Recurring | Active Markets (Level 1)
Fair Value of Financial Instruments
Total	753,416	446,432
Recurring | Active Markets (Level 1) | U.S. Treasury obligations
Fair Value of Financial Instruments
Marketable securities, available-for-sale	478,794	327,552
Recurring | Active Markets (Level 1) | Money market funds
Fair Value of Financial Instruments
Cash equivalents	274,622	118,880
Recurring | Observable Inputs (Level 2)
Fair Value of Financial Instruments
Total	422,416	497,143
Recurring | Observable Inputs (Level 2) | U.S. government agency securities
Fair Value of Financial Instruments
Marketable securities, available-for-sale	$ 422,416	$ 497,143