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Investment Funds (Details) - USD ($) $ in Thousands		3 Months Ended		18 Months Ended
Investment Funds (Details) - USD ($) $ in Thousands	Jul. 01, 2022	Mar. 31, 2025	Mar. 31, 2024	Jun. 30, 2022	Dec. 31, 2024
Schedule of Equity Method Investments [Line Items]
Unfunded commitments		$ 270,000
Investment funds		1,480,322			$ 1,468,246
Income (Loss) from Investment Funds		27,023	$ (29,349)
Written premiums ceded		550,637	511,464
Fair Value
Schedule of Equity Method Investments [Line Items]
Trading account receivables from brokers and clearing organizations		$ 343,796			60,327
Lifson Re
Schedule of Equity Method Investments [Line Items]
Percentage of reinsurance placements of share placed amounts	30.00%	32.50%		22.50%
Written premiums ceded		$ 171,000	94,000
Financial services
Schedule of Equity Method Investments [Line Items]
Investment funds		183,637			178,685
Income (Loss) from Investment Funds		4,965	5,356
Transportation
Schedule of Equity Method Investments [Line Items]
Investment funds		436,259			430,163
Income (Loss) from Investment Funds		7,114	(13,491)
Real Estate
Schedule of Equity Method Investments [Line Items]
Investment funds		280,722			286,426
Income (Loss) from Investment Funds		8,615	(28,661)
Energy
Schedule of Equity Method Investments [Line Items]
Investment funds		40,256			42,776
Income (Loss) from Investment Funds		(2,102)	8,632
Infrastructure
Schedule of Equity Method Investments [Line Items]
Investment funds		154,761			151,560
Income (Loss) from Investment Funds		3,502	5,039
Other funds
Schedule of Equity Method Investments [Line Items]
Investment funds		384,687			378,636
Income (Loss) from Investment Funds		4,929	$ (6,224)
Deferred compensation trust assets		$ 40,000			$ 38,000