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Investment Information - Investments in operating affiliates (Details) € / shares in Units, $ / shares in Units, € in Millions, $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2024 USD ($) | Dec. 31, 2023 USD ($) | Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($) $ / shares | Dec. 31, 2021 EUR (€) € / shares
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Investment in operating affiliates | $ 1,240 | $ 1,119 |  |  |
Income (loss) from operating affiliates | $ 200 | 184 | $ 75 |  |
Coface |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Percentage ownership | 29.90% |  |  | 29.50% | 29.50%
Investment in affiliate, price per share | € / shares |  |  |  |  | € 9.95
Equity method investment, aggregate cost |  |  |  | $ 546 | € 453
Operating affiliate gain on acquisition |  |  |  | 75 |
Operating affiliates , deferred gain on acquisition |  |  |  | $ 36 |
Operating affiliates, deferred gain on acquisition, amortization period |  |  |  | 5 years |
Investment in operating affiliates | $ 592 | 570 |  |  |
Coface | Issued Shares Excluding Treasury Stock |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Percentage ownership | 30.03% |  |  |  |
Greysbridge Holdings Ltd |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Percentage ownership |  |  |  | 40.00% | 40.00%
Investment in affiliate, price per share | $ / shares |  |  |  | $ 35.00 |
Equity method investment, aggregate cost |  |  |  | $ 279 |
Operating affiliate gain on acquisition |  |  |  | $ 96 |
Investment in operating affiliates | $ 523 | $ 430 |  |  |
Greysbridge Holdings Ltd | Kelso And Company |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Percentage ownership |  |  |  | 30.00% | 30.00%
Greysbridge Holdings Ltd | Warburg Pincus LLC |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Percentage ownership |  |  |  | 30.00% | 30.00%

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