v3.26.3
Fair Value Measurements (Details) - Fair Value Hierarchy - USD ($)
$ in Millions
Sep. 30, 2026
Dec. 31, 2025
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Fixed maturities, at fair value $ 89,372 $ 89,833
Equity securities, at fair value 640 618
Other Investments, at fair value 9 9
Held for sale investments, at fair value   3,347
Total invested assets measured on a recurring basis 90,021 93,807
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    
Fixed maturities, at fair value 3,022 3,857
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    
Fixed maturities, at fair value 30,541 31,378
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    
Fixed maturities, at fair value 408 312
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    
Fixed maturities, at fair value 12,507 13,232
Corporate and all other bonds [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Fixed maturities, at fair value 42,894 41,054
Common stock [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Equity securities, at fair value 607 584
Non-redeemable preferred stock [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Equity securities, at fair value 33 34
Level 1 [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Fixed maturities, at fair value 3,022 3,882
Equity securities, at fair value 606 583
Other Investments, at fair value 9 9
Held for sale investments, at fair value   104
Total invested assets measured on a recurring basis 3,637 4,578
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    
Fixed maturities, at fair value 3,022 3,857
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    
Fixed maturities, at fair value 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    
Fixed maturities, at fair value 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    
Fixed maturities, at fair value 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    
Fixed maturities, at fair value 0 25
Level 1 [Member] | Common stock [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Equity securities, at fair value 598 576
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    
Equity securities, at fair value 8 7
Level 2 [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Fixed maturities, at fair value 86,271 85,620
Equity securities, at fair value 3 3
Other Investments, at fair value 0 0
Held for sale investments, at fair value   3,243
Total invested assets measured on a recurring basis 86,274 88,866
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    
Fixed maturities, at fair value 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    
Fixed maturities, at fair value 30,541 31,378
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    
Fixed maturities, at fair value 408 312
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    
Fixed maturities, at fair value 12,507 13,232
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    
Fixed maturities, at fair value 42,815 40,698
Level 2 [Member] | Common stock [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Equity securities, at fair value 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    
Equity securities, at fair value 3 3
Level 3 [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Fixed maturities, at fair value 79 331
Equity securities, at fair value 31 32
Other Investments, at fair value 0 0
Held for sale investments, at fair value   0
Total invested assets measured on a recurring basis 110 363
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    
Fixed maturities, at fair value 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    
Fixed maturities, at fair value 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    
Fixed maturities, at fair value 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    
Fixed maturities, at fair value 0 0
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    
Fixed maturities, at fair value 79 331
Level 3 [Member] | Common stock [Member]    
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured    
Equity securities, at fair value 9 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    
Equity securities, at fair value 22 24
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    
Equity securities, at fair value $ 31 $ 32