Equity Method Investments and Other - Schedule of Net Investment Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Schedule of Equity Method Investments [Line Items]
Net investment income	$ 30,727	$ 18,704	$ 57,782	$ 38,126
Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Net investment income	(1,057)	(898)	(2,354)	(2,886)
RISCOM \| Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Net investment income	326	1,055	1,045	927
Dowling Capital Partners LP units \| Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Net investment income	14	203	189	216
Hudson Ventures Fund II LP units \| Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Net investment income	1	90	(105)	65
Brewer Lane Ventures Fund II LP \| Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Net investment income	(25)	(27)	(37)	143
JVM Funds LLC \| Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Net investment income	(175)	(304)	(606)	(515)
Arena SOP LP units \| Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Net investment income	0	(218)	0	(1,474)
Arena Special Opportunities Fund, LP units \| Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Net investment income	$ (1,198)	$ (1,697)	$ (2,840)	$ (2,248)