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Postretirement benefits (Narrative) (Details) - USD ($) $ in Millions |  | 12 Months Ended
--- | --- | ---
Oct. 31, 2016 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Expenses recognized during period under the defined contributions plans |  | $ 283 | $ 230 | $ 214
Defined Benefit Plan, Plan Amendment [Abstract] |  |  |  |
Other investments |  | 5,527 | 1,341 |
Pension Plan [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined Benefit Plan, Accumulated Benefit Obligation |  | 3,500 | 3,400 |
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year |  | 15 |  |
Other Postretirement Benefits Plan [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined Benefit Plan, Plan Assets, Amount |  | 69 | 81 | 119
Actuarial Loss (gain) |  | 2 | (4) |
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation |  | 21 | 18 |
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year |  | 1 |  |
Defined Benefit Plan, Plan Amendment [Abstract] |  |  |  |
(Increase) decrease in other comprehensive income, curtailment |  | 0 | 0 | 0
Amortization of Prior Service Cost (Credit) |  | $ 0 | 0 | 26
Defined Benefit Plan, Equity Securities [Member] | Minimum |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Percentage |  | 55.00% |  |
Defined Benefit Plan, Equity Securities [Member] | Maximum |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Percentage |  | 65.00% |  |
Level 2 | Fixed Maturities [Member] | Other Postretirement Benefits Plan [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined Benefit Plan, Plan Assets, Amount |  | $ 34 | 50 |
Other Investments | Other Postretirement Benefits Plan [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined Benefit Plan, Plan Assets, Amount |  | 35 | 31 |
UNITED STATES | Pension Plan [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined Benefit Plan, Plan Assets, Amount |  | 3,589 | 3,316 | 4,151
Actuarial Loss (gain) |  | 82 | (890) |
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation |  | 45 | 66 |
Defined Benefit Plan, Plan Amendment [Abstract] |  |  |  |
(Increase) decrease in other comprehensive income, curtailment |  | 0 | 0 | 0
Amortization of Prior Service Cost (Credit) |  | 0 | 0 | 0
Other investments |  | 634 | 538 |
UNITED STATES | Postretirement Health Coverage [Member] |  |  |  |
Defined Benefit Plan, Plan Amendment [Abstract] |  |  |  |
Effect of Plan Amendment on Accumulated Benefit Obligation | $ 383 |  |  |
Amortization of Prior Service Cost (Credit) |  |  |  | 26
UNITED STATES | Postretirement Health Coverage [Member] | Subject to Amortization [Member] |  |  |  |
Defined Benefit Plan, Plan Amendment [Abstract] |  |  |  |
Effect of Plan Amendment on Accumulated Benefit Obligation | $ 410 |  |  |
Non - U.S. | Pension Plan [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined Benefit Plan, Plan Assets, Amount |  | 986 | 938 | 1,318
Actuarial Loss (gain) |  | 29 | (391) |
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation |  | 73 | 61 |
Defined Benefit Plan, Plan Amendment [Abstract] |  |  |  |
(Increase) decrease in other comprehensive income, curtailment |  | 0 | 0 | 0
Amortization of Prior Service Cost (Credit) |  | (1) | 0 | $ 0
Other investments |  | $ 227 | $ 201 |

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