Investments - Unrealized Gains or (Losses) Included in Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gains (Losses) included in Other Comprehensive Income for Assets Held at the End of the Period	$ (8,308)	$ 14,386	$ 32,600
Asset- backed Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gains (Losses) included in Other Comprehensive Income for Assets Held at the End of the Period	63	(173)	708
Collateralized debt obligations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gains (Losses) included in Other Comprehensive Income for Assets Held at the End of the Period	12,447	(2,523)	1,514
Corporates
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gains (Losses) included in Other Comprehensive Income for Assets Held at the End of the Period	$ (20,818)	$ 17,082	$ 30,378