Investment Information - Operating affiliates (Details) € / shares in Units, $ / shares in Units, $ in Thousands, € in Millions	12 Months Ended
	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2021 EUR (€) € / shares	Dec. 30, 2021	Jul. 01, 2021 $ / shares
Schedule of Equity Method Investments [Line Items]
Investment in operating affiliates	$ 1,135,655	$ 129,291
Income (loss) from operating affiliates	$ 264,693	$ 16,766	$ 2,233
Greysbridge Holdings Ltd | Kelso And Company
Schedule of Equity Method Investments [Line Items]
Percentage ownership						30.00%
Greysbridge Holdings Ltd | Warburg Pincus
Schedule of Equity Method Investments [Line Items]
Percentage ownership						30.00%
Coface
Schedule of Equity Method Investments [Line Items]
Percentage ownership	29.86%			29.86%	29.50%
Investment in affiliate, price per share | € / shares				€ 9.95
Equity method investment, aggregate cost	$ 546,000			€ 453
Operating affiliate gain on acquisition	74,500
Operating affiliates , deferred gain on acquisition	$ 36,000
Operating affiliates, deferred gain on acquisition, amortization period	5 years
Investment in operating affiliates	$ 630,500
Coface | Issued Shares Excluding Treasury Stock
Schedule of Equity Method Investments [Line Items]
Percentage ownership	30.10%			30.10%
Greysbridge Holdings Ltd
Schedule of Equity Method Investments [Line Items]
Percentage ownership						40.00%
Investment in affiliate, price per share | $ / shares						$ 35.00
Equity method investment, aggregate cost	$ 278,900
Operating affiliate gain on acquisition	95,700
Investment in operating affiliates	375,700
Gain (loss) on deconsolidation	$ (33,100)