Restricted Investments (Details) $ in Thousands	Oct. 01, 2020	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Restricted Investments Note [Abstract]
Guaranteed interest rate on deposit (as a percent)	0.04
Restricted investments		$ 433,307	$ 487,587
Restricted investments, long-term		$ 188,857	$ 306,601

Investments which are not defined as or included in marketable (debt, equity, or other) securities whose use is restricted in whole or in part, generally by contractual agreements or regulatory requirements. For use in an unclassified balance sheet.

No definition available.

Name:	us-gaap_RestrictedInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant