v3.25.2
Fair Value Measurements (Details) - Fair Value Hierarchy - Recurring basis [Member] - USD ($)
$ in Millions
Jun. 30, 2025
Dec. 31, 2024
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis $ 88,241 $ 84,373
Fixed maturities [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 87,569 83,666
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 3,843 5,570
Obligations of U.S. states, municipalities and political subdivisions [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 28,560 27,185
Debt securities issued by foreign governments [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 978 909
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 13,112 12,605
Corporate and all other bonds [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 41,076 37,397
Equity securities [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 651 687
Common stock [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 608 639
Non-redeemable preferred stock [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 43 48
Other Investments [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 21 20
Level 1 [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 4,485 6,237
Level 1 [Member] | Fixed maturities [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 3,847 5,570
Level 1 [Member] | U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 3,843 5,570
Level 1 [Member] | Obligations of U.S. states, municipalities and political subdivisions [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 0 0
Level 1 [Member] | Debt securities issued by foreign governments [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 0 0
Level 1 [Member] | Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 0 0
Level 1 [Member] | Corporate and all other bonds [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 4 0
Level 1 [Member] | Equity securities [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 617 647
Level 1 [Member] | Common stock [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 601 631
Level 1 [Member] | Non-redeemable preferred stock [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 16 16
Level 1 [Member] | Other Investments [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 21 20
Level 2 [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 83,483 77,850
Level 2 [Member] | Fixed maturities [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 83,480 77,847
Level 2 [Member] | U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 0 0
Level 2 [Member] | Obligations of U.S. states, municipalities and political subdivisions [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 28,560 27,185
Level 2 [Member] | Debt securities issued by foreign governments [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 978 909
Level 2 [Member] | Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 13,109 12,602
Level 2 [Member] | Corporate and all other bonds [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 40,833 37,151
Level 2 [Member] | Equity securities [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 3 3
Level 2 [Member] | Common stock [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 0 0
Level 2 [Member] | Non-redeemable preferred stock [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 3 3
Level 2 [Member] | Other Investments [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 0 0
Level 3 [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 273 286
Level 3 [Member] | Fixed maturities [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 242 249
Level 3 [Member] | U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 0 0
Level 3 [Member] | Obligations of U.S. states, municipalities and political subdivisions [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 0 0
Level 3 [Member] | Debt securities issued by foreign governments [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 0 0
Level 3 [Member] | Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 3 3
Level 3 [Member] | Corporate and all other bonds [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 239 246
Level 3 [Member] | Equity securities [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 31 37
Level 3 [Member] | Common stock [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 7 8
Level 3 [Member] | Non-redeemable preferred stock [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 24 29
Level 3 [Member] | Investment in non-public common and preferred equity securities where the fair value estimate is determined either internally or by an external fund manager [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis 31 37
Level 3 [Member] | Other Investments [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Total invested assets measured on a recurring basis $ 0 $ 0