Supplemental Reinsurance Premiums (Schedule of Property and Liability Insurance Earned Premiums) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Abstract]
Direct amounts	$ 4,022,611	$ 3,793,664	$ 3,603,780
Ceded to other companies	(80,950)	(65,017)	(56,212)
Assumed	10,821	13,301	8,067
Net premiums earned	$ 3,952,482	$ 3,741,948	$ 3,555,635