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Investment Information - Investment in operating affiliates (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2023 | Jun. 30, 2022 | Jun. 30, 2023 | Jun. 30, 2022 | Dec. 31, 2022
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Investment in operating affiliates | $ 973 |  | $ 973 |  | $ 965
Income (loss) from operating affiliates | $ 22 | $ 5 | $ 61 | $ 30 |
Coface |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Percentage ownership | 29.90% |  | 29.90% |  |
Investment in operating affiliates | $ 518 |  | $ 518 |  | 563
Greysbridge Holdings Ltd |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Percentage ownership | 40.00% |  | 40.00% |  |
Investment in operating affiliates | $ 339 |  | $ 339 |  | $ 306
Issued Shares Excluding Treasury Stock | Coface |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Percentage ownership | 30.00% |  | 30.00% |  |

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