Statutory Requirements - Statutory Net Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Bermuda
Statutory Accounting Practices [Line Items]
Statutory Net Income (Loss)	$ (700,666)	$ (89,267)	$ 836,707
Switzerland
Statutory Accounting Practices [Line Items]
Statutory Net Income (Loss)	(237,003)	80,500	71,829
U.K.
Statutory Accounting Practices [Line Items]
Statutory Net Income (Loss)	(24,573)	(46,352)	(37,427)
U.S.
Statutory Accounting Practices [Line Items]
Statutory Net Income (Loss)	$ 35,344	$ 10,465	$ 17,403