Fair Value Measurements - Assets and liabilities measured and carried at fair value in the financial statements (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Assets:
Available for sale (AFS) fixed maturities	$ 10,568	$ 10,398
Trading fixed maturities	71	76
Equity securities	770	751
Assets of managed investment entities	3,848	4,140
Other assets	70	82
Total assets accounted for at fair value	15,257	15,366
Liabilities:
Liabilities of managed investment entities	3,726	3,965
Derivative liability	14	18
Total liabilities accounted for at fair value	3,741	3,985
Contingent consideration — acquisitions
Liabilities:
Fair value of potential contingent consideration	1	2
Other liabilities — derivatives
Liabilities:
Derivative liability	14	18
Fixed maturities
Assets:
Available for sale (AFS) fixed maturities	10,568	10,398
Trading fixed maturities	71	76
U.S. government and government agencies
Assets:
Available for sale (AFS) fixed maturities	180	173
States, municipalities and political subdivisions
Assets:
Available for sale (AFS) fixed maturities	875	859
Foreign government
Assets:
Available for sale (AFS) fixed maturities	241	237
Residential MBS
Assets:
Available for sale (AFS) fixed maturities	2,118	1,989
Commercial MBS
Assets:
Available for sale (AFS) fixed maturities	41	51
Collateralized loan obligations
Assets:
Available for sale (AFS) fixed maturities	1,241	1,237
Other asset-backed securities
Assets:
Available for sale (AFS) fixed maturities	2,381	2,356
Corporate and other
Assets:
Available for sale (AFS) fixed maturities	3,491	3,496
Equity securities
Assets:
Equity securities	770	751
Other assets
Assets:
Other assets		1
Level 1
Assets:
Assets of managed investment entities	372	419
Total assets accounted for at fair value	998	1,023
Liabilities:
Liabilities of managed investment entities	361	402
Total liabilities accounted for at fair value	361	402
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	192	185
Trading fixed maturities	0	0
Level 1 | U.S. government and government agencies
Assets:
Available for sale (AFS) fixed maturities	180	173
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	12	12
Level 1 | Equity securities
Assets:
Equity securities	434	419
Level 1 | Other assets
Assets:
Other assets		0
Level 2
Assets:
Assets of managed investment entities	3,464	3,711
Total assets accounted for at fair value	13,189	13,247
Liabilities:
Liabilities of managed investment entities	3,354	3,553
Total liabilities accounted for at fair value	3,368	3,571
Level 2 | Contingent consideration — acquisitions
Liabilities:
Fair value of potential contingent consideration	0	0
Level 2 | Other liabilities — derivatives
Liabilities:
Derivative liability	14	18
Level 2 | Fixed maturities
Assets:
Available for sale (AFS) fixed maturities	9,628	9,445
Trading fixed maturities	58	50
Level 2 | U.S. government and government agencies
Assets:
Available for sale (AFS) fixed maturities	0	0
Level 2 | States, municipalities and political subdivisions
Assets:
Available for sale (AFS) fixed maturities	871	858
Level 2 | Foreign government
Assets:
Available for sale (AFS) fixed maturities	241	237
Level 2 | Residential MBS
Assets:
Available for sale (AFS) fixed maturities	2,117	1,988
Level 2 | Commercial MBS
Assets:
Available for sale (AFS) fixed maturities	41	51
Level 2 | Collateralized loan obligations
Assets:
Available for sale (AFS) fixed maturities	1,241	1,237
Level 2 | Other asset-backed securities
Assets:
Available for sale (AFS) fixed maturities	2,100	2,060
Level 2 | Corporate and other
Assets:
Available for sale (AFS) fixed maturities	3,017	3,014
Level 2 | Equity securities
Assets:
Equity securities	39	40
Level 2 | Other assets
Assets:
Other assets		1
Level 3
Assets:
Assets of managed investment entities	12	10
Total assets accounted for at fair value	1,070	1,096
Liabilities:
Liabilities of managed investment entities	11	10
Total liabilities accounted for at fair value	12	12
Level 3 | Contingent consideration — acquisitions
Liabilities:
Fair value of potential contingent consideration	1	2
Level 3 | Other liabilities — derivatives
Liabilities:
Derivative liability	0	0
Level 3 | Fixed maturities
Assets:
Available for sale (AFS) fixed maturities	748	768
Trading fixed maturities	13	26
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	4	1
Level 3 | Foreign government
Assets:
Available for sale (AFS) fixed maturities	0	0
Level 3 | Residential MBS
Assets:
Available for sale (AFS) fixed maturities	1	1
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	0	0
Level 3 | Other asset-backed securities
Assets:
Available for sale (AFS) fixed maturities	281	296
Level 3 | Corporate and other
Assets:
Available for sale (AFS) fixed maturities	462	470
Level 3 | Equity securities
Assets:
Equity securities	$ 297	292
Level 3 | Other assets
Assets:
Other assets		$ 0