Historical Loss and LAE Development - Reserve Development (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
(Favorable)/Unfavorable Reserve Development
Prior accident years	$ (108,547)	$ (122,579)	$ (125,463)
Casualty Segment
(Favorable)/Unfavorable Reserve Development
Prior accident years	(78,498)	(87,225)	(108,632)
Property segment
(Favorable)/Unfavorable Reserve Development
Prior accident years	(21,196)	(24,927)	(10,981)
Surety Segment
(Favorable)/Unfavorable Reserve Development
Prior accident years	$ (8,853)	$ (10,427)	$ (5,850)