Investment Information - Investment in operating affiliates (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Schedule of Equity Method Investments [Line Items]
Investment in operating affiliates	$ 1,000		$ 1,000		$ 965
Income (loss) from operating affiliates	$ 54	$ 9	$ 115	$ 39
Coface
Schedule of Equity Method Investments [Line Items]
Percentage ownership	29.90%		29.90%
Investment in operating affiliates	$ 521		$ 521		563
Greysbridge Holdings Ltd
Schedule of Equity Method Investments [Line Items]
Percentage ownership	40.00%		40.00%
Investment in operating affiliates	$ 362		$ 362		$ 306
Issued Shares Excluding Treasury Stock | Coface
Schedule of Equity Method Investments [Line Items]
Percentage ownership	30.00%		30.00%