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Related party transactions (Schedule of related party transactions) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Related Party Transaction [Line Items] |  |  |
Other (income) expense | $ (836) | $ 89 | $ (2,367)
Private equities | 14,078 | 12,355 |
Ceded Premiums Written | 10,165 | 10,258 | 8,912
Losses and loss expenses | 24,100 | 22,572 | 21,030
Insurance and reinsurance balances payable | 8,302 | 7,780 |
Total revenues | $ 49,735 | $ 43,097 | 40,869
Bermuda | ABR Reinsurance Capital Holdings Ltd. [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Ownership Percentage | 19.00% | 19.00% |
Bermuda | ABR Reinsurance Capital Holdings Ltd. [Member] | ABR Reinsurance Capital Holdings Ltd. [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Ownership Percentage | 18.70% |  |
ABR Reinsurance Capital Holdings Ltd. [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Warrants & Rights Outstanding | 0.50% |  |
Ceded Premiums Written | $ 441 | $ 507 | 442
Commissions received | 119 | 138 | 133
Reinsurance Recoverable on Losses and Loss Expenses | 1,241 | 1,050 |
Insurance and reinsurance balances payable | 40 | 110 |
BlackRock, Inc. | Related Party |  |  |
Related Party Transaction [Line Items] |  |  |
Total revenues | 8 | 7 | 11
Aquiline Capital Partners LLC |  |  |
Related Party Transaction [Line Items] |  |  |
Investment Company, Financial Commitment to Investee, Future Amount | 182 |  |
Other (income) expense | 36 | 8 | 68
Private equities | 368 | 271 |
Starr Technical Risk Agency and Affiliates [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Premiums Written, Gross | 216 | 618 | 592
Ceded Premiums Written | 115 | 353 | 321
Paid commissions | 38 | 122 | 114
Commissions received | 26 | 79 | 73
Losses and loss expenses | 180 | 225 | $ 157
Reinsurance Recoverable on Losses and Loss Expenses | 503 | 541 |
Insurance and reinsurance balances payable | $ 44 | $ 96 |

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