INVESTMENTS - Schedule of Amortized Cost, Allowance for Credit Losses, Gross Unrealized Appreciation/(Depreciation) and Fair Value of Fixed Maturity Securities (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Fixed maturity securities - available for sale
Amortized Cost	$ 29,311	$ 28,568
Allowance for Credit Losses	(46)	(48)	$ (62)	$ (54)
Unrealized Appreciation	240	358
Unrealized Depreciation	(1,209)	(1,137)
Fair Value	28,297	27,740
Fixed maturity securities - held to maturity
Amortized Cost	849	864
Allowance for Credit Losses	(9)	(8)	(9)	(9)
Unrealized Appreciation	15	12
Unrealized Depreciation	(13)	(13)
Fair Value	842	854
U.S. Treasury securities and obligations of U.S. government agencies and corporations
Fixed maturity securities - available for sale
Amortized Cost	1,042	1,045
Allowance for Credit Losses	0	0
Unrealized Appreciation	3	3
Unrealized Depreciation	(52)	(52)
Fair Value	993	996
Obligations of U.S. states and political subdivisions
Fixed maturity securities - available for sale
Amortized Cost	125	138
Allowance for Credit Losses	0	0
Unrealized Appreciation	1	1
Unrealized Depreciation	(10)	(11)
Fair Value	115	128
Corporate Securities
Fixed maturity securities - available for sale
Amortized Cost	8,192	7,587
Allowance for Credit Losses	(45)	(47)	(55)	(45)
Unrealized Appreciation	94	135
Unrealized Depreciation	(329)	(322)
Fair Value	7,912	7,353
Fixed maturity securities - held to maturity
Amortized Cost	175	150
Allowance for Credit Losses	(2)	(2)	(2)	(2)
Unrealized Appreciation	5	1
Unrealized Depreciation	(4)	(3)
Fair Value	173	146
Asset-backed Securities
Fixed maturity securities - available for sale
Amortized Cost	5,310	5,644
Allowance for Credit Losses	0	0
Unrealized Appreciation	27	25
Unrealized Depreciation	(33)	(51)
Fair Value	5,305	5,618
Fixed maturity securities - held to maturity
Amortized Cost	569	609
Allowance for Credit Losses	(5)	(5)	(6)	(6)
Unrealized Appreciation	4	4
Unrealized Depreciation	(9)	(10)
Fair Value	559	597
Commercial
Fixed maturity securities - available for sale
Amortized Cost	1,064	1,091
Allowance for Credit Losses	0	0
Unrealized Appreciation	1	1
Unrealized Depreciation	(84)	(92)
Fair Value	981	1,000
Fixed maturity securities - held to maturity
Amortized Cost	21	21
Allowance for Credit Losses	0	0
Unrealized Appreciation	0	0
Unrealized Depreciation	0	0
Fair Value	21	21
Agency Residential
Fixed maturity securities - available for sale
Amortized Cost	4,835	4,869
Allowance for Credit Losses	0	0
Unrealized Appreciation	30	55
Unrealized Depreciation	(280)	(229)
Fair Value	4,585	4,695
Non-agency Residential
Fixed maturity securities - available for sale
Amortized Cost	668	431
Allowance for Credit Losses	0	0
Unrealized Appreciation	8	14
Unrealized Depreciation	(4)	(2)
Fair Value	672	443
Foreign government securities
Fixed maturity securities - available for sale
Amortized Cost	2,240	2,042
Allowance for Credit Losses	0	0
Unrealized Appreciation	16	33
Unrealized Depreciation	(131)	(108)
Fair Value	2,124	1,967
Foreign corporate securities
Fixed maturity securities - available for sale
Amortized Cost	5,835	5,720
Allowance for Credit Losses	0	(1)	(7)	(10)
Unrealized Appreciation	60	92
Unrealized Depreciation	(285)	(271)
Fair Value	5,609	5,540
Fixed maturity securities - held to maturity
Amortized Cost	84	84
Allowance for Credit Losses	(1)	(1)	$ (1)	$ (1)
Unrealized Appreciation	6	7
Unrealized Depreciation	0	0
Fair Value	$ 89	$ 90

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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