Other Long-Term Investments - Net Investment Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Schedule of Equity Method Investments [Line Items]
Net investment income	$ 4,646	$ 15,149
Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Net investment income	(4,664)	9,210
Arena SOP LP units | Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Net investment income	(2,051)	6,117
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	(1,730)	2,804
Dowling Capital Partners LP units | Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Net investment income	267	514
Hudson Ventures Fund 2 LP units | Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Net investment income	(255)	64
JVM Funds LLC | Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Net investment income	(420)	186
RISCOM | Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Net investment income	81	18
Universa Black Swan LP units | Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Net investment income	$ (556)	$ (493)