Fair Value Measurements - Assets and liabilities measured and carried at fair value in the financial statements (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Assets:
Available for sale (AFS) fixed maturities	$ 10,377	$ 10,095
Trading fixed maturities	57	32
Equity securities, at fair value	1,018	1,010
Assets of managed investment entities	4,484	5,447
Other assets — derivatives	87	40
Total assets accounted for at fair value	15,942	16,584
Liabilities:
Liabilities of managed investment entities	4,307	5,332
Other liabilities — derivatives	22	42
Total liabilities accounted for at fair value	4,331	5,399
Contingent consideration - acquisitions
Liabilities:
Contingent consideration — acquisitions	2	25
Other liabilities — derivatives
Liabilities:
Other liabilities — derivatives	22	42
Fixed maturities
Assets:
Available for sale (AFS) fixed maturities	10,377	10,095
Trading fixed maturities	57	32
U.S. Government and government agencies
Assets:
Available for sale (AFS) fixed maturities	236	219
States, municipalities and political subdivisions
Assets:
Available for sale (AFS) fixed maturities	984	1,186
Foreign government
Assets:
Available for sale (AFS) fixed maturities	230	226
Residential MBS
Assets:
Available for sale (AFS) fixed maturities	1,658	1,598
Commercial MBS
Assets:
Available for sale (AFS) fixed maturities	74	85
Collateralized loan obligations
Assets:
Available for sale (AFS) fixed maturities	1,687	1,921
Other asset-backed securities
Assets:
Available for sale (AFS) fixed maturities	2,362	2,245
Corporate and other
Assets:
Available for sale (AFS) fixed maturities	3,146	2,615
Equity securities
Assets:
Equity securities, at fair value	1,018	1,010
Other assets
Assets:
Other assets — derivatives	6
Level 1
Assets:
Assets of managed investment entities	335	659
Total assets accounted for at fair value	1,079	1,442
Liabilities:
Liabilities of managed investment entities	322	645
Total liabilities accounted for at fair value	322	645
Level 1 | Contingent consideration - acquisitions
Liabilities:
Contingent consideration — acquisitions	0	0
Level 1 | Other liabilities — derivatives
Liabilities:
Other liabilities — derivatives	0	0
Level 1 | Fixed maturities
Assets:
Available for sale (AFS) fixed maturities	244	227
Trading fixed maturities	0	0
Level 1 | U.S. Government and government agencies
Assets:
Available for sale (AFS) fixed maturities	235	219
Level 1 | States, municipalities and political subdivisions
Assets:
Available for sale (AFS) fixed maturities	0	0
Level 1 | Foreign government
Assets:
Available for sale (AFS) fixed maturities	0	0
Level 1 | Residential MBS
Assets:
Available for sale (AFS) fixed maturities	0	0
Level 1 | Commercial MBS
Assets:
Available for sale (AFS) fixed maturities	0	0
Level 1 | Collateralized loan obligations
Assets:
Available for sale (AFS) fixed maturities	0	0
Level 1 | Other asset-backed securities
Assets:
Available for sale (AFS) fixed maturities	0	0
Level 1 | Corporate and other
Assets:
Available for sale (AFS) fixed maturities	9	8
Level 1 | Equity securities
Assets:
Equity securities, at fair value	500	556
Level 1 | Other assets
Assets:
Other assets — derivatives	0
Level 2
Assets:
Assets of managed investment entities	4,140	4,777
Total assets accounted for at fair value	13,633	14,040
Liabilities:
Liabilities of managed investment entities	3,976	4,676
Total liabilities accounted for at fair value	3,998	4,718
Level 2 | Contingent consideration - acquisitions
Liabilities:
Contingent consideration — acquisitions	0	0
Level 2 | Other liabilities — derivatives
Liabilities:
Other liabilities — derivatives	22	42
Level 2 | Fixed maturities
Assets:
Available for sale (AFS) fixed maturities	9,397	9,204
Trading fixed maturities	57	32
Level 2 | U.S. Government and government agencies
Assets:
Available for sale (AFS) fixed maturities	1	0
Level 2 | States, municipalities and political subdivisions
Assets:
Available for sale (AFS) fixed maturities	982	1,181
Level 2 | Foreign government
Assets:
Available for sale (AFS) fixed maturities	230	226
Level 2 | Residential MBS
Assets:
Available for sale (AFS) fixed maturities	1,656	1,589
Level 2 | Commercial MBS
Assets:
Available for sale (AFS) fixed maturities	74	85
Level 2 | Collateralized loan obligations
Assets:
Available for sale (AFS) fixed maturities	1,686	1,919
Level 2 | Other asset-backed securities
Assets:
Available for sale (AFS) fixed maturities	2,011	1,916
Level 2 | Corporate and other
Assets:
Available for sale (AFS) fixed maturities	2,757	2,288
Level 2 | Equity securities
Assets:
Equity securities, at fair value	33	27
Level 2 | Other assets
Assets:
Other assets — derivatives	6
Level 3
Assets:
Assets of managed investment entities	9	11
Total assets accounted for at fair value	1,230	1,102
Liabilities:
Liabilities of managed investment entities	9	11
Total liabilities accounted for at fair value	11	36
Level 3 | Contingent consideration - acquisitions
Liabilities:
Contingent consideration — acquisitions	2	25
Level 3 | Other liabilities — derivatives
Liabilities:
Other liabilities — derivatives	0	0
Level 3 | Fixed maturities
Assets:
Available for sale (AFS) fixed maturities	736	664
Trading fixed maturities	0	0
Level 3 | U.S. Government and government agencies
Assets:
Available for sale (AFS) fixed maturities	0	0
Level 3 | States, municipalities and political subdivisions
Assets:
Available for sale (AFS) fixed maturities	2	5
Level 3 | Foreign government
Assets:
Available for sale (AFS) fixed maturities	0	0
Level 3 | Residential MBS
Assets:
Available for sale (AFS) fixed maturities	2	9
Level 3 | Commercial MBS
Assets:
Available for sale (AFS) fixed maturities	0	0
Level 3 | Collateralized loan obligations
Assets:
Available for sale (AFS) fixed maturities	1	2
Level 3 | Other asset-backed securities
Assets:
Available for sale (AFS) fixed maturities	351	329
Level 3 | Corporate and other
Assets:
Available for sale (AFS) fixed maturities	380	319
Level 3 | Equity securities
Assets:
Equity securities, at fair value	485	$ 427
Level 3 | Other assets
Assets:
Other assets — derivatives	$ 0