Restricted Cash and Cash Equivalents - Reconciliation of Cash, Cash Equivalents and Restricted Cash and Cash Equivalents (Details) - USD ($)	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2021
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 141,020,000	$ 95,073,000	$ 91,645,000
Restricted cash and cash equivalents - current	0
Restricted cash and investments - non-current	130,729,000	111,691,000	89,760,000
Less Restricted investments - non-current	(65,565,000)		(60,032,000)
Total cash, cash equivalents and restricted cash and cash equivalents shown in the statement of cash flows	$ 206,184,000	$ 143,843,000	$ 121,373,000	$ 548,322,000