Reinsurance (Schedule of Reinsurance Ceded and Recoveries) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Premium Written :
Direct	$ 601,780	$ 549,077	$ 514,223
Assumed	2,376
Ceded premiums written	(238,573)	(187,248)	(157,279)
Net premiums written	365,583	361,829	356,944
Premium Earned:
Direct	567,089	524,229	494,643
Assumed	1,680
Ceded	(207,732)	(170,859)	(145,562)
Premiums Earned, Net, Property and Casualty	361,037	353,370	349,081
Reinsurance recoveries	$ 144,948	$ 116,057	$ 89,892