Fair Value Measurements - Schedule of the Carrying Value and Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Assets
Fixed maturity securities, available-for-sale	$ 1,287,466	$ 1,324,476
Equity securities	128,690	119,945
Bank loan participations	173,046	156,169
Cash and cash equivalents	305,496	274,298
Restricted cash equivalents	73,396	72,449	$ 104,254	$ 103,215
Short-term investments	84,534	72,137
Liabilities
Senior debt	222,300	222,300
Junior subordinated debt	104,055	104,055
Carrying Value
Assets
Fixed maturity securities, available-for-sale	1,287,466	1,324,176
Equity securities	128,690	119,945
Bank loan participations	173,046	156,169
Cash and cash equivalents	305,496	274,298
Restricted cash equivalents	73,396	72,449
Short-term investments	84,534	72,137
Other invested assets – notes receivable	12,437	12,174
Liabilities
Senior debt	222,300	222,300
Junior subordinated debt	104,055	104,055
Fair Value
Assets
Fixed maturity securities, available-for-sale	1,287,466	1,324,176
Equity securities	128,690	119,945
Bank loan participations	173,046	156,169
Cash and cash equivalents	305,496	274,298
Restricted cash equivalents	73,396	72,449
Short-term investments	84,534	72,137
Other invested assets – notes receivable	11,582	11,702
Liabilities
Senior debt	231,009	233,408
Junior subordinated debt	$ 135,125	$ 138,264