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Investment Information - Investment in operating affiliates (Details) € / shares in Units, $ / shares in Units, $ in Thousands, € in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2021 EUR (€) € / shares	Jul. 01, 2021 $ / shares
Schedule of Equity Method Investments [Line Items]
Time lag for reporting			3 months
Investment in operating affiliates	$ 891,212		$ 891,212		$ 1,135,655
Income (loss) from operating affiliates	$ 8,507	$ 124,119	$ 37,665	$ 224,052
Coface
Schedule of Equity Method Investments [Line Items]
Percentage ownership	29.86%		29.86%		29.50%	29.50%
Investment in affiliate, price per share | € / shares						€ 9.95
Operating affiliate, aggregate cost					$ 546,000	€ 453
Investment in operating affiliates	$ 506,700		$ 506,700		630,500
Operating affiliate, gain on acquisition					74,500
Greysbridge Holdings Ltd
Schedule of Equity Method Investments [Line Items]
Percentage ownership							40.00%
Investment in affiliate, price per share | $ / shares							$ 35.00
Operating affiliate, aggregate cost					278,900
Investment in operating affiliates	$ 277,600		$ 277,600		375,700
Operating affiliate, gain on acquisition					$ 95,700
Issued Shares Excluding Treasury Stock | Coface
Schedule of Equity Method Investments [Line Items]
Percentage ownership	30.05%		30.05%
Kelso And Company | Greysbridge Holdings Ltd
Schedule of Equity Method Investments [Line Items]
Percentage ownership							30.00%
Warburg Pincus LLC | Greysbridge Holdings Ltd
Schedule of Equity Method Investments [Line Items]
Percentage ownership							30.00%

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