Restricted Cash and Investments - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021	Dec. 31, 2020
Restricted Investments Note [Abstract]
Cash and cash equivalents	$ 476,792	$ 579,350	$ 399,551
Bond purchase fund	30,975	0	245,605
Restricted cash included in restricted cash and short-term investments	84,600		0
Total cash, cash equivalents and restricted cash reported in the consolidated statements of cash flows	$ 592,367	$ 581,150	$ 645,156	$ 405,511