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INVESTMENTS - Schedule of Amortized Cost, Allowance for Credit Losses, Gross Unrealized Appreciation/(Depreciation) and Fair Value of Fixed Maturity Securities (Details) - USD ($) $ in Millions	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023
Fixed maturity securities - available for sale
Amortized Cost	$ 19,992		$ 17,685
Allowance for Credit Losses	(40)	$ (37)	(36)	$ (42)	$ (46)	$ (48)
Unrealized Appreciation	262		106
Unrealized Depreciation	(419)		(569)
Fair Value	19,796		17,186
Fixed maturity securities – held to maturity
Amortized Cost	658		765
Allowance for Credit Losses	(7)	(8)	(8)	(8)	(9)	(8)
Unrealized Appreciation	15		14
Unrealized Depreciation	(10)		(12)
Fair Value	657		759
U.S. Treasury securities and obligations of U.S. government agencies and corporations
Fixed maturity securities - available for sale
Amortized Cost	258		266
Allowance for Credit Losses	0		0
Unrealized Appreciation	0		0
Unrealized Depreciation	(9)		(11)
Fair Value	249		255
Obligations of U.S. States and political subdivisions
Fixed maturity securities - available for sale
Amortized Cost	57		75
Allowance for Credit Losses	0		0
Unrealized Appreciation	0		0
Unrealized Depreciation	(7)		(5)
Fair Value	50		70
Corporate securities
Fixed maturity securities - available for sale
Amortized Cost	5,958		4,156
Allowance for Credit Losses	(39)	(36)	(35)	(42)	(45)	(47)
Unrealized Appreciation	105		37
Unrealized Depreciation	(128)		(160)
Fair Value	5,896		3,997
Fixed maturity securities – held to maturity
Amortized Cost	168		177
Allowance for Credit Losses	(2)	(2)	(2)	(2)	(2)	(2)
Unrealized Appreciation	5		5
Unrealized Depreciation	(2)		(4)
Fair Value	169		175
Asset-backed securities
Fixed maturity securities - available for sale
Amortized Cost	4,758		5,321
Allowance for Credit Losses	0	0	0	0	0	0
Unrealized Appreciation	18		24
Unrealized Depreciation	(27)		(35)
Fair Value	4,749		5,311
Fixed maturity securities – held to maturity
Amortized Cost	404		484
Allowance for Credit Losses	(4)	(4)	(4)	(5)	(5)	(5)
Unrealized Appreciation	5		5
Unrealized Depreciation	(7)		(8)
Fair Value	398		477
Commercial
Fixed maturity securities - available for sale
Amortized Cost			479
Allowance for Credit Losses			0
Unrealized Appreciation			0
Unrealized Depreciation			(38)
Fair Value			441
Fixed maturity securities – held to maturity
Amortized Cost	7		21
Allowance for Credit Losses	0		0
Unrealized Appreciation	0		0
Unrealized Depreciation	0		0
Fair Value	7		21
Agency commercial
Fixed maturity securities - available for sale
Amortized Cost	208		0
Allowance for Credit Losses	0
Unrealized Appreciation	3
Unrealized Depreciation	(2)
Fair Value	210		0
Non-agency commercial
Fixed maturity securities - available for sale
Amortized Cost	473		479
Allowance for Credit Losses	0
Unrealized Appreciation	1
Unrealized Depreciation	(27)
Fair Value	447		441
Agency residential
Fixed maturity securities - available for sale
Amortized Cost	3,804		3,306
Allowance for Credit Losses	0		0
Unrealized Appreciation	30		10
Unrealized Depreciation	(126)		(166)
Fair Value	3,708		3,151
Non-agency residential
Fixed maturity securities - available for sale
Amortized Cost	1,353		1,164
Allowance for Credit Losses	0		0
Unrealized Appreciation	24		9
Unrealized Depreciation	(3)		(11)
Fair Value	1,374		1,161
Foreign government securities
Fixed maturity securities - available for sale
Amortized Cost	1,004		1,013
Allowance for Credit Losses	0		0
Unrealized Appreciation	20		8
Unrealized Depreciation	(31)		(52)
Fair Value	992		970
Foreign corporate securities
Fixed maturity securities - available for sale
Amortized Cost	2,121		1,905
Allowance for Credit Losses	0	0	0	0	0	0
Unrealized Appreciation	60		17
Unrealized Depreciation	(60)		(91)
Fair Value	2,121		1,831
Fixed maturity securities – held to maturity
Amortized Cost	79		84
Allowance for Credit Losses	(1)	$ (1)	(1)	$ (1)	$ (1)	$ (1)
Unrealized Appreciation	5		4
Unrealized Depreciation	0		0
Fair Value	$ 83		$ 86