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Fair value measurements (Financial Instruments Measured At Fair Value On Recurring Basis) (Details) - USD ($) $ in Millions | Jun. 30, 2024 | Dec. 31, 2023 | Jun. 30, 2023
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Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |  |
Debt Securities, Available-for-Sale | $ 107,840 |  | $ 106,571 |  |
Equity securities | 3,792 |  | 3,455 |  |
Short-term investments | 4,546 |  | 4,551 |  |
Other Investments | 7,513 |  | 5,527 |  |
Securities lending collateral | 1,889 |  | 1,299 |  |
Separate account assets | 5,834 |  | 5,573 |  | $ 5,574
Market risk benefits | 576 |  | 771 |  |
Private equities | 14,365 |  | 14,078 |  |
Investment Funds Limited Partnerships Partially Owned Investment Companies Fair Value |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |  |
Private equities | 14,365 |  | 14,078 |  |
Policy Loans |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |  |
Other Investments | 1,029 |  | 702 |  |
U.S. Treasury / Agency |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |  |
Debt Securities, Available-for-Sale | 2,741 |  | 3,590 |  |
Non-U.S. |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |  |
Debt Securities, Available-for-Sale | 34,918 |  | 35,164 |  |
Corporate and asset-backed securities |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |  |
Debt Securities, Available-for-Sale | 43,620 |  | 42,830 |  |
Mortgage-backed securities |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |  |
Debt Securities, Available-for-Sale | 24,614 |  | 22,058 |  |
Municipal |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |  |
Debt Securities, Available-for-Sale | 1,947 |  | 2,929 |  |
Level 1 | Fair Value, Recurring |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |  |
Debt Securities, Available-for-Sale | 2,128 |  | 2,911 |  |
Equity securities | 3,692 |  | 3,368 |  |
Short-term investments | 2,822 |  | 1,915 |  |
Other Investments | 581 | [1] | 589 | [2] |
Securities lending collateral | 0 |  | 0 |  |
Investment derivatives | 41 |  | 54 |  |
Derivatives designated as hedging instruments | 0 |  | 0 |  |
Other derivative instruments | 1 |  |  |  |
Separate account assets | 5,749 |  | 5,482 |  |
Total assets measured at fair value | 15,014 | [1],[3] | 14,319 | [2],[4] |
Investment derivatives | 169 |  | 136 |  |
Derivatives designated as hedging instruments | 0 |  | 0 |  |
Other derivative instruments, liability | 2 |  | 37 |  |
Market risk benefits | 0 | [5] | 0 | [6] |
Total liabilities measured at fair value | 171 |  | 173 |  |
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 | 2,128 |  | 2,911 |  |
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 | 102,351 |  | 100,339 |  |
Equity securities | 0 |  | 0 |  |
Short-term investments | 1,712 |  | 2,633 |  |
Other Investments | 5,903 | [1] | 4,236 | [2] |
Securities lending collateral | 1,889 |  | 1,299 |  |
Investment derivatives | 0 |  | 0 |  |
Derivatives designated as hedging instruments | 127 |  | 136 |  |
Other derivative instruments | 0 |  |  |  |
Separate account assets | 85 |  | 91 |  |
Total assets measured at fair value | 112,067 | [1],[3] | 108,734 | [2],[4] |
Investment derivatives | 0 |  | 0 |  |
Derivatives designated as hedging instruments | 96 |  | 128 |  |
Other derivative instruments, liability | 5 |  | 5 |  |
Market risk benefits | 0 | [5] | 0 | [6] |
Total liabilities measured at fair value | 101 |  | 133 |  |
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 | 613 |  | 679 |  |
Level 2 | Non-U.S. | Fair Value, Recurring |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |  |
Debt Securities, Available-for-Sale | 34,286 |  | 34,472 |  |
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 | 40,911 |  | 40,208 |  |
Level 2 | Mortgage-backed securities | Fair Value, Recurring |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |  |
Debt Securities, Available-for-Sale | 24,594 |  | 22,051 |  |
Level 2 | Municipal | Fair Value, Recurring |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |  |
Debt Securities, Available-for-Sale | 1,947 |  | 2,929 |  |
Level 3 | Fair Value, Recurring |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |  |
Debt Securities, Available-for-Sale | 3,361 |  | 3,321 |  |
Equity securities | 100 |  | 87 |  |
Short-term investments | 12 |  | 3 |  |
Other Investments | 0 | [1] | 0 | [2] |
Securities lending collateral | 0 |  | 0 |  |
Investment derivatives | 0 |  | 0 |  |
Derivatives designated as hedging instruments | 0 |  | 0 |  |
Other derivative instruments | 0 |  |  |  |
Separate account assets | 0 |  | 0 |  |
Total assets measured at fair value | 3,473 | [1],[3] | 3,411 | [2],[4] |
Investment derivatives | 0 |  | 0 |  |
Derivatives designated as hedging instruments | 0 |  | 0 |  |
Other derivative instruments, liability | 0 |  | 0 |  |
Market risk benefits | 576 | [5] | 771 | [6] |
Total liabilities measured at fair value | 576 |  | 771 |  |
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 | 632 |  | 692 |  |
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 | 2,709 |  | 2,622 |  |
Level 3 | Mortgage-backed securities | Fair Value, Recurring |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |  |
Debt Securities, Available-for-Sale | 20 |  | 7 |  |
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 | 107,840 |  | 106,571 |  |
Equity securities | 3,792 |  | 3,455 |  |
Short-term investments | 4,546 |  | 4,551 |  |
Other Investments | 6,484 | [1] | 4,825 | [2] |
Securities lending collateral | 1,889 |  | 1,299 |  |
Investment derivatives | 41 |  | 54 |  |
Derivatives designated as hedging instruments | 127 |  | 136 |  |
Other derivative instruments | 1 |  |  |  |
Separate account assets | 5,834 |  | 5,573 |  |
Total assets measured at fair value | 130,554 | [1],[3] | 126,464 | [2],[4] |
Investment derivatives | 169 |  | 136 |  |
Derivatives designated as hedging instruments | 96 |  | 128 |  |
Other derivative instruments, liability | 7 |  | 42 |  |
Market risk benefits | 576 | [5] | 771 | [6] |
Total liabilities measured at fair value | 848 |  | 1,077 |  |
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 | 2,741 |  | 3,590 |  |
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 | 34,918 |  | 35,164 |  |
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 | 43,620 |  | 42,830 |  |
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 | 24,614 |  | 22,058 |  |
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 | $ 1,947 |  | $ 2,929 |  |
[1] | Excluded from the table above are other investments of $1,029 million, principally policy loans, measured using NAV as a practical expedient.
[2] | Excluded from the table above are other investments of $702 million, principally policy loans, measured using NAV as a practical expedient.
[3] | Excluded from the table above are Private equities of $14,365 million, measured using NAV as a practical expedient.
[4] | Excluded from the table above are Private equities of $14,078 million, measured using NAV as a practical expedient.
[5] | Refer to Note 11 for additional information on Market risk benefits.
[6] | Refer to Note 11 for additional information on Market risk benefits.

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- Definition Fair value of investment other than investment in equity security, investment in debt security and equity method investment. Includes, but is not limited to, investment in certain entities that calculate net asset value per share. Example includes, but is not limited to, investment in hedge fund, venture capital fund, private equity fund, and real estate partnership or fund. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 107 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482078/820-10-55-107 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 103 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482078/820-10-55-103 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 100 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482078/820-10-55-100 Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (bbb)(2)(i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (bbb)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (bbb)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 35 -Paragraph 54B -Publisher FASB -URI https://asc.fasb.org/1943274/2147482134/820-10-35-54B Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6A -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A + Details
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