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Investment Funds (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended		18 Months Ended
Investment Funds (Details) - USD ($) $ in Thousands	Jul. 01, 2022	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2022	Dec. 31, 2022
Schedule of Equity Method Investments [Line Items]
Unfunded commitments		$ 401,000		$ 401,000
Investment funds		1,594,225		1,594,225			$ 1,608,548
Income (Loss) from Investment Funds				993	$ 85,874
Written premiums ceded		525,258	$ 466,766	999,751	913,349
Fair Value
Schedule of Equity Method Investments [Line Items]
Trading account receivables from brokers and clearing organizations		484,457		484,457			233,863
Lifson Re
Schedule of Equity Method Investments [Line Items]
Percentage of reinsurance placements of share placed amounts	30.00%					22.50%
Written premiums ceded				281,000	226,000
Financial services
Schedule of Equity Method Investments [Line Items]
Investment funds		216,759		216,759			204,644
Income (Loss) from Investment Funds				2,963	28,243
Transportation
Schedule of Equity Method Investments [Line Items]
Investment funds		432,596		432,596			465,683
Income (Loss) from Investment Funds				(20,321)	24,135
Real Estate
Schedule of Equity Method Investments [Line Items]
Investment funds		333,694		333,694			336,753
Income (Loss) from Investment Funds				23,843	25,355
Energy
Schedule of Equity Method Investments [Line Items]
Investment funds		117,095		117,095			116,432
Income (Loss) from Investment Funds				3,439	3,708
Infrastructure
Schedule of Equity Method Investments [Line Items]
Investment funds		121,965		121,965			115,428
Income (Loss) from Investment Funds				5,936	(133)
Other funds
Schedule of Equity Method Investments [Line Items]
Investment funds		372,116		372,116			369,608
Income (Loss) from Investment Funds				(14,867)	$ 4,566
Deferred compensation trust assets		$ 35,000		$ 35,000			$ 30,000