Investments - Fixed Maturity Securities and Short Term Investments (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021
Schedule of Investments [Line Items]
Percent of Total	100.00%	100.00%
Amortized Cost	$ 7,359	$ 7,707
Allowance for Credit Losses	(69)	(65)	$ (47)	$ (42)
Gross Unrealized Gains	75	65
Gross Unrealized Losses	(496)	(588)
Estimated Fair Value	$ 6,869	$ 7,119
Government agency obligations as a percentage of total mortgage backed securities	32.00%	30.00%
Obligations of state and political subdivisions
Schedule of Investments [Line Items]
Percent of Total	43.00%	45.00%
Amortized Cost	$ 3,161	$ 3,509
Allowance for Credit Losses	(14)	(14)
Gross Unrealized Gains	46	37
Gross Unrealized Losses	(96)	(138)
Estimated Fair Value	$ 3,097	$ 3,394
U.S. government and agencies
Schedule of Investments [Line Items]
Percent of Total	1.00%	2.00%
Amortized Cost	$ 94	$ 118
Allowance for Credit Losses	0	0
Gross Unrealized Gains	1	1
Gross Unrealized Losses	(7)	(8)
Estimated Fair Value	$ 88	$ 111
Corporate securities
Schedule of Investments [Line Items]
Percent of Total	33.00%	31.00%
Amortized Cost	$ 2,408	$ 2,387
Allowance for Credit Losses	(6)	(6)
Gross Unrealized Gains	5	2
Gross Unrealized Losses	(254)	(299)
Estimated Fair Value	$ 2,153	$ 2,084
RMBS
Schedule of Investments [Line Items]
Percent of Total	6.00%	5.00%
Amortized Cost	$ 429	$ 418
Allowance for Credit Losses	(20)	(19)
Gross Unrealized Gains	3	3
Gross Unrealized Losses	(62)	(62)
Estimated Fair Value	$ 350	$ 340
CMBS
Schedule of Investments [Line Items]
Percent of Total	3.00%	4.00%
Amortized Cost	$ 267	$ 282
Allowance for Credit Losses	0	0
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(9)	(11)
Estimated Fair Value	$ 258	$ 271
CLOs and CLO warehouse assets:
Schedule of Investments [Line Items]
Percent of Total	6.00%	6.00%
Amortized Cost	$ 453	$ 449
Allowance for Credit Losses	0	0
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(20)	(21)
Estimated Fair Value	$ 433	$ 428
Others
Schedule of Investments [Line Items]
Percent of Total	6.00%	5.00%
Amortized Cost	$ 426	$ 423
Allowance for Credit Losses	(29)	(26)
Gross Unrealized Gains	20	22
Gross Unrealized Losses	(28)	(26)
Estimated Fair Value	$ 389	$ 393
Non-U.S. government securities
Schedule of Investments [Line Items]
Percent of Total	2.00%	2.00%
Amortized Cost	$ 121	$ 121
Allowance for Credit Losses	0	0
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(20)	(23)
Estimated Fair Value	$ 101	$ 98

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