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Investment Funds (Details) - USD ($) $ in Thousands		3 Months Ended
Investment Funds (Details) - USD ($) $ in Thousands	Jul. 01, 2022	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Schedule of Equity Method Investments [Line Items]
Unfunded commitments		$ 408,000
Investment funds		1,601,567		$ 1,608,548
Income (Loss) from Investment Funds		2,180	$ 52,012
Written premiums ceded		474,493	446,582
Fair Value
Schedule of Equity Method Investments [Line Items]
Trading account receivables from brokers and clearing organizations		$ 583,970		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		$ 107,000	89,000
Financial services
Schedule of Equity Method Investments [Line Items]
Investment funds		216,871		204,644
Income (Loss) from Investment Funds		956	16,364
Transportation
Schedule of Equity Method Investments [Line Items]
Investment funds		444,645		465,683
Income (Loss) from Investment Funds		(13,047)	25,932
Real Estate
Schedule of Equity Method Investments [Line Items]
Investment funds		336,808		336,753
Income (Loss) from Investment Funds		11,788	11,179
Energy
Schedule of Equity Method Investments [Line Items]
Investment funds		117,461		116,432
Income (Loss) from Investment Funds		3,439	(892)
Infrastructure
Schedule of Equity Method Investments [Line Items]
Investment funds		119,042		115,428
Income (Loss) from Investment Funds		3,355	841
Other funds
Schedule of Equity Method Investments [Line Items]
Investment funds		366,740		369,608
Income (Loss) from Investment Funds		(4,311)	$ (1,412)
Deferred compensation trust assets		$ 34,000		$ 30,000