Fair Value Measurements - Assets and liabilities measured and carried at fair value in the financial statements (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Assets:
Available for sale (AFS) fixed maturities	$ 10,196	$ 10,377
Trading fixed maturities	65	57
Equity securities	1,077	1,018
Assets of managed investment entities	4,695	4,484
Other assets	60	87
Total assets accounted for at fair value	16,034	15,942
Liabilities:
Liabilities of managed investment entities	4,536	4,307
Derivative liability	26	22
Total liabilities accounted for at fair value	4,564	4,331
Contingent consideration — acquisitions
Liabilities:
Fair value of potential contingent consideration	2	2
Other liabilities — derivatives
Liabilities:
Derivative liability	26	22
Fixed maturities:
Assets:
Available for sale (AFS) fixed maturities	10,196	10,377
Trading fixed maturities	65	57
U.S. government and government agencies
Assets:
Available for sale (AFS) fixed maturities	176	236
States, municipalities and political subdivisions
Assets:
Available for sale (AFS) fixed maturities	868	984
Foreign government
Assets:
Available for sale (AFS) fixed maturities	231	230
Residential MBS
Assets:
Available for sale (AFS) fixed maturities	1,663	1,658
Commercial MBS
Assets:
Available for sale (AFS) fixed maturities	70	74
Collateralized loan obligations
Assets:
Available for sale (AFS) fixed maturities	1,459	1,687
Other asset-backed securities
Assets:
Available for sale (AFS) fixed maturities	2,363	2,362
Corporate and other
Assets:
Available for sale (AFS) fixed maturities	3,366	3,146
Equity securities
Assets:
Equity securities	1,077	1,018
Other assets
Assets:
Other assets	1	6
Level 1
Assets:
Assets of managed investment entities	558	335
Total assets accounted for at fair value	1,180	1,079
Liabilities:
Liabilities of managed investment entities	539	322
Total liabilities accounted for at fair value	539	322
Level 1 | Contingent consideration — acquisitions
Liabilities:
Fair value of potential contingent consideration	0	0
Level 1 | Other liabilities — derivatives
Liabilities:
Derivative liability	0	0
Level 1 | Fixed maturities:
Assets:
Available for sale (AFS) fixed maturities	187	244
Trading fixed maturities	0	0
Level 1 | U.S. government and government agencies
Assets:
Available for sale (AFS) fixed maturities	176	235
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	11	9
Level 1 | Equity securities
Assets:
Equity securities	435	500
Level 1 | Other assets
Assets:
Other assets	0	0
Level 2
Assets:
Assets of managed investment entities	4,125	4,140
Total assets accounted for at fair value	13,472	13,633
Liabilities:
Liabilities of managed investment entities	3,985	3,976
Total liabilities accounted for at fair value	4,011	3,998
Level 2 | Contingent consideration — acquisitions
Liabilities:
Fair value of potential contingent consideration	0	0
Level 2 | Other liabilities — derivatives
Liabilities:
Derivative liability	26	22
Level 2 | Fixed maturities:
Assets:
Available for sale (AFS) fixed maturities	9,253	9,397
Trading fixed maturities	53	57
Level 2 | U.S. government and government agencies
Assets:
Available for sale (AFS) fixed maturities	0	1
Level 2 | States, municipalities and political subdivisions
Assets:
Available for sale (AFS) fixed maturities	866	982
Level 2 | Foreign government
Assets:
Available for sale (AFS) fixed maturities	231	230
Level 2 | Residential MBS
Assets:
Available for sale (AFS) fixed maturities	1,661	1,656
Level 2 | Commercial MBS
Assets:
Available for sale (AFS) fixed maturities	70	74
Level 2 | Collateralized loan obligations
Assets:
Available for sale (AFS) fixed maturities	1,458	1,686
Level 2 | Other asset-backed securities
Assets:
Available for sale (AFS) fixed maturities	2,023	2,011
Level 2 | Corporate and other
Assets:
Available for sale (AFS) fixed maturities	2,944	2,757
Level 2 | Equity securities
Assets:
Equity securities	40	33
Level 2 | Other assets
Assets:
Other assets	1	6
Level 3
Assets:
Assets of managed investment entities	12	9
Total assets accounted for at fair value	1,382	1,230
Liabilities:
Liabilities of managed investment entities	12	9
Total liabilities accounted for at fair value	14	11
Level 3 | Contingent consideration — acquisitions
Liabilities:
Fair value of potential contingent consideration	2	2
Level 3 | Other liabilities — derivatives
Liabilities:
Derivative liability	0	0
Level 3 | Fixed maturities:
Assets:
Available for sale (AFS) fixed maturities	756	736
Trading fixed maturities	12	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	2
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	2
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	1
Level 3 | Other asset-backed securities
Assets:
Available for sale (AFS) fixed maturities	340	351
Level 3 | Corporate and other
Assets:
Available for sale (AFS) fixed maturities	411	380
Level 3 | Equity securities
Assets:
Equity securities	602	485
Level 3 | Other assets
Assets:
Other assets	$ 0	$ 0