Investments - Unrealized Gains or (Losses) Included in Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
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	$ (40,169)	$ (15,496)
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	0	(1,261)
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	(3,809)	9,900
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	$ (36,360)	$ (24,135)