Restricted Cash and Cash Equivalents - Reconciliation of Cash, Cash Equivalents and Restricted Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents	$ 289,391	$ 283,524	$ 32,414
Restricted cash and cash equivalents - current	29,317		27,865
Restricted cash and investments - non-current	39,924	37,338	27,271
Less Restricted investments - non-current	(37,940)		(24,969)
Total cash, cash equivalents and restricted cash and cash equivalents shown in the statement of cash flows	$ 320,692	$ 311,853	$ 62,581	$ 67,472