Supplemental Reinsurance Premiums (Schedule of Property and Liability Insurance Earned Premiums) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Abstract]
Direct amounts	$ 4,368,342	$ 4,022,611	$ 3,793,664
Ceded to other companies	(109,445)	(80,950)	(65,017)
Assumed	15,481	10,821	13,301
Net premiums earned	$ 4,274,378	$ 3,952,482	$ 3,741,948