Fair Value Measurements (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Level 2
Liabilities:
Fair value of liability	$ 863,300
Recurring
Financial Assets:
Total financial assets	984,299	$ 717,596
Recurring | Money market deposits
Financial Assets:
Total financial assets	55,703	28,990
Recurring | U.S. Treasury securities
Financial Assets:
Total financial assets	787,875	597,744
Recurring | Corporate bonds and notes
Financial Assets:
Total financial assets	52,721	12,328
Recurring | Municipal securities
Financial Assets:
Total financial assets	88,000	78,534
Recurring | Level 1
Financial Assets:
Total financial assets	843,578	626,734
Recurring | Level 1 | Money market deposits
Financial Assets:
Total financial assets	55,703	28,990
Recurring | Level 1 | U.S. Treasury securities
Financial Assets:
Total financial assets	787,875	597,744
Recurring | Level 2
Financial Assets:
Total financial assets	140,721	90,862
Recurring | Level 2 | Corporate bonds and notes
Financial Assets:
Total financial assets	52,721	12,328
Recurring | Level 2 | Municipal securities
Financial Assets:
Total financial assets	$ 88,000	$ 78,534