Statutory Requirements - Statutory Net Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Bermuda
Statutory Accounting Practices [Line Items]
Statutory Net Income (Loss)	$ 2,904,049	$ (700,666)	$ (89,267)
Switzerland
Statutory Accounting Practices [Line Items]
Statutory Net Income (Loss)	233,904	(237,003)	80,500
U.K.
Statutory Accounting Practices [Line Items]
Statutory Net Income (Loss)	158,258	(24,573)	(46,352)
U.S.
Statutory Accounting Practices [Line Items]
Statutory Net Income (Loss)	$ (17,268)	$ 35,344	$ 10,465