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Investments - Fixed Maturity Securities and Short Term Investments (Details) - USD ($) $ in Millions	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022
Schedule of Investments [Line Items]
Percent of Total	100.00%		100.00%
Amortized Cost	$ 6,478		$ 6,746
Allowance for Credit Losses	(69)	$ (67)	(77)	$ (79)	$ (69)	$ (65)
Gross Unrealized Gains	38		55
Gross Unrealized Losses	(441)		(417)
Estimated Fair Value	$ 6,006		$ 6,307
Government agency obligations as a percentage of total mortgage backed securities	61.00%		42.00%
Obligations of state and political subdivisions
Schedule of Investments [Line Items]
Percent of Total	35.00%		41.00%
Amortized Cost	$ 2,239		$ 2,733
Allowance for Credit Losses	(14)		(13)
Gross Unrealized Gains	25		33
Gross Unrealized Losses	(105)		(92)
Estimated Fair Value	$ 2,145		$ 2,661
U.S. government and agencies
Schedule of Investments [Line Items]
Percent of Total	1.00%		1.00%
Amortized Cost	$ 77		$ 65
Allowance for Credit Losses	0		0
Gross Unrealized Gains	1		1
Gross Unrealized Losses	(6)		(6)
Estimated Fair Value	$ 72		$ 60
Corporate securities
Schedule of Investments [Line Items]
Percent of Total	37.00%		34.00%
Amortized Cost	$ 2,358		$ 2,327
Allowance for Credit Losses	(6)		(6)
Gross Unrealized Gains	8		17
Gross Unrealized Losses	(214)		(197)
Estimated Fair Value	$ 2,146		$ 2,141
RMBS
Schedule of Investments [Line Items]
Percent of Total	9.00%		6.00%
Amortized Cost	$ 565		$ 428
Allowance for Credit Losses	(21)		(21)
Gross Unrealized Gains	2		3
Gross Unrealized Losses	(69)		(68)
Estimated Fair Value	$ 477		$ 342
CMBS
Schedule of Investments [Line Items]
Percent of Total	3.00%		2.00%
Amortized Cost	$ 204		$ 157
Allowance for Credit Losses	0		0
Gross Unrealized Gains	0		0
Gross Unrealized Losses	(6)		(6)
Estimated Fair Value	$ 198		$ 151
CLOs
Schedule of Investments [Line Items]
Percent of Total	6.00%		7.00%
Amortized Cost	$ 412		$ 456
Allowance for Credit Losses	0		0
Gross Unrealized Gains	1		1
Gross Unrealized Losses	(2)		(7)
Estimated Fair Value	$ 411		$ 450
Others
Schedule of Investments [Line Items]
Percent of Total	8.00%		7.00%
Amortized Cost	$ 538		$ 465
Allowance for Credit Losses	(28)		(37)
Gross Unrealized Gains	1		0
Gross Unrealized Losses	(24)		(26)
Estimated Fair Value	$ 487		$ 402
Non-U.S. government securities
Schedule of Investments [Line Items]
Percent of Total	1.00%		2.00%
Amortized Cost	$ 85		$ 115
Allowance for Credit Losses	0		0
Gross Unrealized Gains	0		0
Gross Unrealized Losses	(15)		(15)
Estimated Fair Value	$ 70		$ 100

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