Supplemental Reinsurance Premiums (Schedule of Property and Liability Insurance Earned Premiums) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Abstract]
Direct amounts	$ 3,793,664	$ 3,603,780	$ 3,655,233
Ceded to other companies	(65,017)	(56,212)	(56,725)
Assumed	13,301	8,067	910
Net amounts	$ 3,741,948	$ 3,555,635	$ 3,599,418