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Investment Information - Investment in operating affiliates (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Schedule of Equity Method Investments [Line Items]
Investment in operating affiliates	$ 1,417		$ 1,417		$ 1,240
Income (loss) from operating affiliates	$ 62	$ 36	$ 119	$ 136
Coface
Schedule of Equity Method Investments [Line Items]
Percentage ownership	29.90%		29.90%
Investment in operating affiliates	$ 683		$ 683		592
Greysbridge Holdings Ltd
Schedule of Equity Method Investments [Line Items]
Percentage ownership	40.00%		40.00%
Investment in operating affiliates	$ 613		$ 613		$ 523
Issued Shares Excluding Treasury Stock | Coface
Schedule of Equity Method Investments [Line Items]
Percentage ownership	30.00%		30.00%

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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