Investments - Fixed Maturity Securities and Short Term Investments (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024	Dec. 31, 2023
Schedule of Investments [Line Items]
Percent of Total	100.00%	100.00%
Amortized Cost	$ 6,774	$ 6,827
Allowance for Credit Losses	(45)	(60)	$ (67)	$ (77)
Gross Unrealized Gains	57	44
Gross Unrealized Losses	(371)	(442)
Estimated Fair Value	$ 6,415	$ 6,369
Government agency obligations as a percentage of total mortgage backed securities	68.00%	68.00%
Obligations of state and political subdivisions
Schedule of Investments [Line Items]
Percent of Total	29.00%	30.00%
Amortized Cost	$ 2,003	$ 2,032
Allowance for Credit Losses	(14)	(14)
Gross Unrealized Gains	27	25
Gross Unrealized Losses	(92)	(103)
Estimated Fair Value	$ 1,924	$ 1,940
U.S. government and agencies
Schedule of Investments [Line Items]
Percent of Total	1.00%	1.00%
Amortized Cost	$ 76	$ 72
Allowance for Credit Losses	0	0
Gross Unrealized Gains	1	1
Gross Unrealized Losses	(5)	(6)
Estimated Fair Value	$ 72	$ 67
Corporate securities
Schedule of Investments [Line Items]
Percent of Total	39.00%	38.00%
Amortized Cost	$ 2,630	$ 2,586
Allowance for Credit Losses	(7)	(7)
Gross Unrealized Gains	17	9
Gross Unrealized Losses	(163)	(206)
Estimated Fair Value	$ 2,477	$ 2,382
RMBS
Schedule of Investments [Line Items]
Percent of Total	10.00%	9.00%
Amortized Cost	$ 649	$ 657
Allowance for Credit Losses	(22)	(21)
Gross Unrealized Gains	5	2
Gross Unrealized Losses	(63)	(71)
Estimated Fair Value	$ 569	$ 567
CMBS
Schedule of Investments [Line Items]
Percent of Total	3.00%	3.00%
Amortized Cost	$ 183	$ 189
Allowance for Credit Losses	0	0
Gross Unrealized Gains	1	0
Gross Unrealized Losses	(2)	(3)
Estimated Fair Value	$ 182	$ 186
CLOs
Schedule of Investments [Line Items]
Percent of Total	8.00%	9.00%
Amortized Cost	$ 571	$ 615
Allowance for Credit Losses	(1)	(1)
Gross Unrealized Gains	3	6
Gross Unrealized Losses	(31)	(9)
Estimated Fair Value	$ 542	$ 611
Others
Schedule of Investments [Line Items]
Percent of Total	9.00%	9.00%
Amortized Cost	$ 581	$ 593
Allowance for Credit Losses	(1)	(17)
Gross Unrealized Gains	2	1
Gross Unrealized Losses	(4)	(30)
Estimated Fair Value	578	547
Others | Affiliated Entity
Schedule of Investments [Line Items]
Amortized Cost	41	41
Estimated Fair Value	$ 42	$ 42
Non-U.S. government securities
Schedule of Investments [Line Items]
Percent of Total	1.00%	1.00%
Amortized Cost	$ 81	$ 83
Allowance for Credit Losses	0	0
Gross Unrealized Gains	1	0
Gross Unrealized Losses	(11)	(14)
Estimated Fair Value	$ 71	$ 69