Fair Value Measurements - Fair Value by Hierarchy (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	$ 39,818	$ 36,231
Fixed maturities, at fair value using the fair value option ("FVO")	327	333
Equity securities, at fair value	864	1,801
Derivative assets	(1)	34
Short-term investments	3,850	3,859
Total assets accounted for at fair value on a recurring basis	44,858	42,258
Liabilities accounted for at fair value on a recurring basis
Derivative liabilities	8	13
Total liabilities accounted for at fair value on a recurring basis	8	13
Credit derivatives
Assets accounted for at fair value on a recurring basis
Derivative assets	(10)	2
Liabilities accounted for at fair value on a recurring basis
Derivative liabilities	10	(2)
Foreign exchange derivatives
Assets accounted for at fair value on a recurring basis
Derivative assets	9	32
Liabilities accounted for at fair value on a recurring basis
Derivative liabilities	4	21
Interest rate derivatives
Liabilities accounted for at fair value on a recurring basis
Derivative liabilities	(6)	(6)
Asset-backed securities ("ABS")
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	3,320	1,941
CLO
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	3,090	2,941
Fixed maturities, at fair value using the fair value option ("FVO")	167	178
Commercial mortgage-backed securities ("CMBS")
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	3,125	3,368
Corporate
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	17,866	15,233
Foreign government/government agencies
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	562	547
Municipal
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	6,039	6,296
Residential mortgage-backed securities ("RMBS")
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	4,287	3,708
U.S. Treasuries
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	1,529	2,197
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	18	0
Fixed maturities, at fair value using the fair value option ("FVO")	0	0
Equity securities, at fair value	333	1,261
Derivative assets	0	0
Short-term investments	1,400	1,429
Total assets accounted for at fair value on a recurring basis	1,751	2,690
Liabilities accounted for at fair value on a recurring basis
Derivative liabilities	0	0
Total liabilities accounted for at fair value on a recurring basis	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Credit derivatives
Assets accounted for at fair value on a recurring basis
Derivative assets	0	0
Liabilities accounted for at fair value on a recurring basis
Derivative liabilities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign exchange derivatives
Assets accounted for at fair value on a recurring basis
Derivative assets	0	0
Liabilities accounted for at fair value on a recurring basis
Derivative liabilities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest rate derivatives
Liabilities accounted for at fair value on a recurring basis
Derivative liabilities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Asset-backed securities ("ABS")
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | CLO
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Commercial mortgage-backed securities ("CMBS")
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign government/government agencies
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Municipal
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Residential mortgage-backed securities ("RMBS")
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasuries
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	18	0
Significant Observable Inputs (Level 2)
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	37,563	34,180
Fixed maturities, at fair value using the fair value option ("FVO")	160	155
Equity securities, at fair value	473	479
Derivative assets	(1)	34
Short-term investments	2,425	2,237
Total assets accounted for at fair value on a recurring basis	40,620	37,085
Liabilities accounted for at fair value on a recurring basis
Derivative liabilities	8	13
Total liabilities accounted for at fair value on a recurring basis	8	13
Significant Observable Inputs (Level 2) | Credit derivatives
Assets accounted for at fair value on a recurring basis
Derivative assets	(10)	2
Liabilities accounted for at fair value on a recurring basis
Derivative liabilities	10	(2)
Significant Observable Inputs (Level 2) | Foreign exchange derivatives
Assets accounted for at fair value on a recurring basis
Derivative assets	9	32
Liabilities accounted for at fair value on a recurring basis
Derivative liabilities	4	21
Significant Observable Inputs (Level 2) | Interest rate derivatives
Liabilities accounted for at fair value on a recurring basis
Derivative liabilities	(6)	(6)
Significant Observable Inputs (Level 2) | Asset-backed securities ("ABS")
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	3,320	1,911
Significant Observable Inputs (Level 2) | CLO
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	2,977	2,826
Significant Observable Inputs (Level 2) | Commercial mortgage-backed securities ("CMBS")
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	2,898	3,146
Significant Observable Inputs (Level 2) | Corporate
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	16,005	13,644
Significant Observable Inputs (Level 2) | Foreign government/government agencies
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	562	547
Significant Observable Inputs (Level 2) | Municipal
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	6,039	6,296
Significant Observable Inputs (Level 2) | Residential mortgage-backed securities ("RMBS")
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	4,251	3,613
Significant Observable Inputs (Level 2) | U.S. Treasuries
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	1,511	2,197
Significant Unobservable Inputs (Level 3)
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	2,237	2,051
Fixed maturities, at fair value using the fair value option ("FVO")	167	178
Equity securities, at fair value	58	61
Derivative assets	0	0
Short-term investments	25	193
Total assets accounted for at fair value on a recurring basis	2,487	2,483
Liabilities accounted for at fair value on a recurring basis
Derivative liabilities	0	0
Total liabilities accounted for at fair value on a recurring basis	0	0
Significant Unobservable Inputs (Level 3) | Credit derivatives
Assets accounted for at fair value on a recurring basis
Derivative assets	0	0
Liabilities accounted for at fair value on a recurring basis
Derivative liabilities	0	0
Significant Unobservable Inputs (Level 3) | Foreign exchange derivatives
Assets accounted for at fair value on a recurring basis
Derivative assets	0	0
Liabilities accounted for at fair value on a recurring basis
Derivative liabilities	0	0
Significant Unobservable Inputs (Level 3) | Interest rate derivatives
Liabilities accounted for at fair value on a recurring basis
Derivative liabilities	0	0
Significant Unobservable Inputs (Level 3) | Asset-backed securities ("ABS")
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	0	30
Significant Unobservable Inputs (Level 3) | CLO
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	113	115
Significant Unobservable Inputs (Level 3) | Commercial mortgage-backed securities ("CMBS")
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	227	222
Significant Unobservable Inputs (Level 3) | Corporate
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	1,861	1,589
Significant Unobservable Inputs (Level 3) | Foreign government/government agencies
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	0	0
Significant Unobservable Inputs (Level 3) | Municipal
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	0	0
Significant Unobservable Inputs (Level 3) | Residential mortgage-backed securities ("RMBS")
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	36	95
Significant Unobservable Inputs (Level 3) | U.S. Treasuries
Assets accounted for at fair value on a recurring basis
Total fixed maturities, AFS	0	0
Fair Value Measured at Net Asset Value Per Share [Member]
Liabilities accounted for at fair value on a recurring basis
Deposit Assets	$ 75	$ 62