v3.26.3
Fair value measurements (Financial Instruments Measured At Fair Value On Recurring Basis) (Details) - USD ($)
$ in Millions
Sep. 30, 2026
Dec. 31, 2025
Sep. 30, 2025
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale $ 125,804 $ 122,680  
Equity securities 10,760 10,801  
Short-term investments 5,293 4,840  
Other investments 10,861 10,749  
Securities lending collateral 2,295 2,500  
Separate account assets 7,340 6,925 $ 6,810
Market risk benefits 530 659  
Private equities 17,528 17,239  
Reserved alternative investment fund      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Equity securities 5,260 5,519  
Other Investments      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Other investments 1,990 1,435  
Investment Funds Limited Partnerships Partially Owned Investment Companies Fair Value      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Private equities 17,528 17,239  
U.S. and local government securities      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale 3,387 3,714  
Non-U.S.      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale 42,466 40,356  
Corporate and asset-backed securities      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale 47,142 47,886  
Mortgage-backed securities      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale 32,809 30,724  
Level 1 | Fair Value, Recurring      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale 1,359 1,481  
Equity securities 5,385 [1] 5,163 [2]  
Short-term investments 2,634 2,657  
Other investments 687 [3] 630 [4]  
Securities lending collateral 0 0  
Investment derivatives 138 22  
Derivatives designated as hedging instruments 0 0  
Other derivative instruments 10 11  
Separate account assets 7,267 6,858  
Total assets measured at fair value 17,480 [1],[3],[5] 16,822 [2],[4],[6]  
Investment derivatives 166 242  
Derivatives designated as hedging instruments 0 0  
Other derivative instruments, liability 3 0  
Market risk benefits 0 [7] 0 [8]  
Total liabilities measured at fair value 169 242  
Level 1 | U.S. and local government securities | Fair Value, Recurring      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale 1,359 1,481  
Level 1 | Non-U.S. | Fair Value, Recurring      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale 0 0  
Level 1 | Corporate and asset-backed securities | Fair Value, Recurring      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale 0 0  
Level 1 | Mortgage-backed securities | Fair Value, Recurring      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale 0 0  
Level 2 | Fair Value, Recurring      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale 119,980 116,982  
Equity securities 0 [1] 0 [2]  
Short-term investments 2,644 2,138  
Other investments 8,184 [3] 8,684 [4]  
Securities lending collateral 2,295 2,500  
Investment derivatives 0 0  
Derivatives designated as hedging instruments 233 266  
Other derivative instruments 0 0  
Separate account assets 73 67  
Total assets measured at fair value 133,409 [1],[3],[5] 130,637 [2],[4],[6]  
Investment derivatives 0 0  
Derivatives designated as hedging instruments 243 232  
Other derivative instruments, liability 0 4  
Market risk benefits 0 [7] 0 [8]  
Total liabilities measured at fair value 243 236  
Level 2 | U.S. and local government securities | Fair Value, Recurring      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale 2,028 2,233  
Level 2 | Non-U.S. | Fair Value, Recurring      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale 41,753 39,685  
Level 2 | Corporate and asset-backed securities | Fair Value, Recurring      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale 43,502 44,340  
Level 2 | Mortgage-backed securities | Fair Value, Recurring      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale 32,697 30,724  
Level 3 | Fair Value, Recurring      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale 4,465 4,217  
Equity securities 115 [1] 119 [2]  
Short-term investments 15 45  
Other investments 0 [3] 0 [4]  
Securities lending collateral 0 0  
Investment derivatives 0 0  
Derivatives designated as hedging instruments 0 0  
Other derivative instruments 0 0  
Separate account assets 0 0  
Total assets measured at fair value 4,595 [1],[3],[5] 4,381 [2],[4],[6]  
Investment derivatives 0 0  
Derivatives designated as hedging instruments 0 0  
Other derivative instruments, liability 0 0  
Market risk benefits 530 [7] 659 [8]  
Total liabilities measured at fair value 530 659  
Level 3 | U.S. and local government securities | Fair Value, Recurring      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale 0 0  
Level 3 | Non-U.S. | Fair Value, Recurring      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale 713 671  
Level 3 | Corporate and asset-backed securities | Fair Value, Recurring      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale 3,640 3,546  
Level 3 | Mortgage-backed securities | Fair Value, Recurring      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale 112 0  
Total Level 1, Level 2, and Level 3 | Fair Value, Recurring      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale 125,804 122,680  
Equity securities 5,500 [1] 5,282 [2]  
Short-term investments 5,293 4,840  
Other investments 8,871 [3] 9,314 [4]  
Securities lending collateral 2,295 2,500  
Investment derivatives 138 22  
Derivatives designated as hedging instruments 233 266  
Other derivative instruments 10 11  
Separate account assets 7,340 6,925  
Total assets measured at fair value 155,484 [1],[3],[5] 151,840 [2],[4],[6]  
Investment derivatives 166 242  
Derivatives designated as hedging instruments 243 232  
Other derivative instruments, liability 3 4  
Market risk benefits 530 [7] 659 [8]  
Total liabilities measured at fair value 942 1,137  
Total Level 1, Level 2, and Level 3 | U.S. and local government securities | Fair Value, Recurring      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale 3,387 3,714  
Total Level 1, Level 2, and Level 3 | Non-U.S. | Fair Value, Recurring      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale 42,466 40,356  
Total Level 1, Level 2, and Level 3 | Corporate and asset-backed securities | Fair Value, Recurring      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale 47,142 47,886  
Total Level 1, Level 2, and Level 3 | Mortgage-backed securities | Fair Value, Recurring      
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]      
Debt Securities, Available-for-Sale $ 32,809 $ 30,724  
[1] Excluded from the table above are funds of $5,260 million, measured using NAV as a practical expedient.
[2] Excluded from the table above are funds of $5,519 million, measured using NAV as a practical expedient.
[3] Excluded from the table above are other investments of $1,990 million, principally investments measured using NAV as a practical expedient and policy loans.
[4] Excluded from the table above are other investments of $1,435 million, principally investments measured using NAV as a practical expedient and policy loans.
[5] Excluded from the table above are private equities of $17,528 million, measured using NAV as a practical expedient.
[6] Excluded from the table above are private equities of $17,239 million, measured using NAV as a practical expedient.
[7] Refer to Note 10 for additional information on Market risk benefits.
[8] Refer to Note 10 for additional information on Market risk benefits.