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Fair value measurements (Financial Instruments Measured At Fair Value On Recurring Basis) (Details) - USD ($) $ in Millions | Sep. 30, 2023 | Dec. 31, 2022
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Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |
Debt Securities, Available-for-Sale | $ 99,766 |  | $ 85,220 |
Equity securities, at fair value | 3,395 |  | 827 |
Other Short-Term Investments | 5,454 |  | 4,960 |
Other investments | 5,583 |  | 1,341 |
Securities lending collateral | 1,469 |  | 1,523 |
Separate account assets | 5,306 |  | 5,190 |
Market risk benefits | 770 |  | 800 |
Alternative Investment | 13,362 |  | 12,355 |
Investment Funds Limited Partnerships Partially Owned Investment Companies Fair Value |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |
Alternative Investment | 13,362 |  | 12,355 |
Policy Loans |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |
Other investments | 603 |  | 343 |
Other Investments |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |
Other investments | 47 |  | 47 |
U.S. Treasury / Agency |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |
Debt Securities, Available-for-Sale | 3,681 |  | 2,626 |
Non-U.S. |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |
Debt Securities, Available-for-Sale | 32,717 |  | 25,908 |
Corporate and asset-backed securities |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |
Debt Securities, Available-for-Sale | 40,855 |  | 36,955 |
Mortgage-backed securities |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |
Debt Securities, Available-for-Sale | 19,605 |  | 15,851 |
Municipal |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |
Debt Securities, Available-for-Sale | 2,908 |  | 3,880 |
Level 1 | Fair Value, Recurring |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |
Debt Securities, Available-for-Sale | 3,084 |  | 2,100 |
Equity securities, at fair value | 3,310 |  | 737 |
Other Short-Term Investments | 2,546 |  | 3,108 |
Other investments | 569 | [1] | 552 | [2]
Securities lending collateral | 0 |  | 0 |
Investment derivative instruments | 42 |  | 82 |
Derivatives designated as hedging instruments | 0 |  | 0 |
Other derivative instruments | 53 |  | 33 |
Separate account assets | 5,217 |  | 5,101 |
Total assets measured at fair value | 14,821 | [1] | 11,713 | [2]
Investment derivatives | 168 |  | 139 |
Derivatives designated as hedging instruments | 0 |  | 0 |
Other derivative instruments, liability | 0 |  |  |
Market risk benefits | 0 | [3] | 0 | [4]
Total liabilities measured at fair value | 168 |  | 139 |
Level 1 | U.S. Treasury / Agency | Fair Value, Recurring |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |
Debt Securities, Available-for-Sale | 3,084 |  | 2,100 |
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 1 | Municipal | 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 | 93,455 |  | 80,096 |
Equity securities, at fair value | 0 |  | 0 |
Other Short-Term Investments | 2,906 |  | 1,849 |
Other investments | 4,364 | [1] | 399 | [2]
Securities lending collateral | 1,469 |  | 1,523 |
Investment derivative instruments | 0 |  | 0 |
Derivatives designated as hedging instruments | 48 |  | 17 |
Other derivative instruments | 0 |  | 0 |
Separate account assets | 89 |  | 89 |
Total assets measured at fair value | 102,331 | [1] | 83,973 | [2]
Investment derivatives | 0 |  | 0 |
Derivatives designated as hedging instruments | 68 |  | 53 |
Other derivative instruments, liability | 4 |  |  |
Market risk benefits | 0 | [3] | 0 | [4]
Total liabilities measured at fair value | 72 |  | 53 |
Level 2 | U.S. Treasury / Agency | Fair Value, Recurring |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |
Debt Securities, Available-for-Sale | 597 |  | 526 |
Level 2 | Non-U.S. | Fair Value, Recurring |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |
Debt Securities, Available-for-Sale | 32,084 |  | 25,344 |
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 | 38,286 |  | 34,506 |
Level 2 | Mortgage-backed securities | Fair Value, Recurring |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |
Debt Securities, Available-for-Sale | 19,580 |  | 15,840 |
Level 2 | Municipal | Fair Value, Recurring |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |
Debt Securities, Available-for-Sale | 2,908 |  | 3,880 |
Level 3 | Fair Value, Recurring |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |
Debt Securities, Available-for-Sale | 3,227 |  | 3,024 |
Equity securities, at fair value | 85 |  | 90 |
Other Short-Term Investments | 2 |  | 3 |
Other investments | 0 | [1] | 0 | [2]
Securities lending collateral | 0 |  | 0 |
Investment derivative instruments | 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 | 3,314 | [1] | 3,117 | [2]
Investment derivatives | 0 |  | 0 |
Derivatives designated as hedging instruments | 0 |  | 0 |
Other derivative instruments, liability | 0 |  |  |
Market risk benefits | 770 | [3] | 800 | [4]
Total liabilities measured at fair value | 770 |  | 800 |
Level 3 | U.S. Treasury / Agency | 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 | 633 |  | 564 |
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 | 2,569 |  | 2,449 |
Level 3 | Mortgage-backed securities | Fair Value, Recurring |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |
Debt Securities, Available-for-Sale | 25 |  | 11 |
Level 3 | Municipal | Fair Value, Recurring |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |
Debt Securities, Available-for-Sale | 0 |  | 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 | 99,766 |  | 85,220 |
Equity securities, at fair value | 3,395 |  | 827 |
Other Short-Term Investments | 5,454 |  | 4,960 |
Other investments | 4,933 | [1] | 951 | [2]
Securities lending collateral | 1,469 |  | 1,523 |
Investment derivative instruments | 42 |  | 82 |
Derivatives designated as hedging instruments | 48 |  | 17 |
Other derivative instruments | 53 |  | 33 |
Separate account assets | 5,306 |  | 5,190 |
Total assets measured at fair value | 120,466 | [1] | 98,803 | [2]
Investment derivatives | 168 |  | 139 |
Derivatives designated as hedging instruments | 68 |  | 53 |
Other derivative instruments, liability | 4 |  |  |
Market risk benefits | 770 | [3] | 800 | [4]
Total liabilities measured at fair value | 1,010 |  | 992 |
Total Level 1, Level 2, and Level 3 | U.S. Treasury / Agency | Fair Value, Recurring |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |
Debt Securities, Available-for-Sale | 3,681 |  | 2,626 |
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 | 32,717 |  | 25,908 |
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 | 40,855 |  | 36,955 |
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 | 19,605 |  | 15,851 |
Total Level 1, Level 2, and Level 3 | Municipal | Fair Value, Recurring |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |
Debt Securities, Available-for-Sale | $ 2,908 |  | $ 3,880 |
[1] | Excluded from the table above are policy loans of $603 million, and other investments of $47 million at September 30, 2023, measured using NAV as a practical expedient.(2)Excluded from the table above are partially-owned investments, investment funds, and limited partnerships of $13,362 million at September 30, 2023, measured using NAV as a practical expedient.
[2] | Excluded from the table above are policy loans of $343 million and other investments of $47 million at December 31, 2022, measured using NAV as a practical expedient.(2)Excluded from the table above are partially-owned investments, investment funds, and limited partnerships of $12,355 million at December 31, 2022, measured using NAV as a practical expedient.
[3] | Refer to Note 11 for additional information on Market risk benefits.
[4] | Refer to Note 11 for additional information on Market risk benefits.

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