Income Taxes - Effective Tax Rate Reconciliation and Pretax Income (Loss) and Revenue by Tax Jurisdiction (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Pre-tax Income Taxes and Revenue [Line Items]
Expected tax provision (benefit)	$ 23	$ (2)	$ 43	$ 12
Tax-exempt interest	(3)	(4)	(6)	(7)
NCI	0	(5)	(3)	(6)
State taxes	4	4	7	8
Foreign taxes	(4)	9	1	10
Stock based compensation	(1)	2	0	4
Other	(1)	(1)	(1)	0
Total provision (benefit) for income taxes	$ 18	$ 3	$ 41	$ 21
Effective tax rate	12.60%	(12.90%)	15.60%	30.30%
Pretax income (loss)	$ 144	$ (22)	$ 264	$ 71
Revenues	360	90	643	390
United States
Pre-tax Income Taxes and Revenue [Line Items]
Pretax income (loss)	117	25	225	109
Revenues	293	106	528	375
Bermuda
Pre-tax Income Taxes and Revenue [Line Items]
Pretax income (loss)	33	(10)	58	17
Revenues	58	6	93	39
U.K.
Pre-tax Income Taxes and Revenue [Line Items]
Pretax income (loss)	(4)	(31)	(15)	(45)
Revenues	8	(18)	21	(18)
Other
Pre-tax Income Taxes and Revenue [Line Items]
Pretax income (loss)	(2)	(6)	(4)	(10)
Revenues	$ 1	$ (4)	$ 1	$ (6)