Schedule VI - Supplemental Information Concerning Property-Casualty Insurance Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Information For Property, Casualty Insurance Underwriters [Abstract]
Deferred Policy Acquisition Costs	$ 16,002	$ 19,193	$ 20,366
Reserves for Unpaid Claims and Claim Adjustment Expenses	527,100	481,567	450,878
Unearned Premiums	276,642	241,254	216,407
Earned Premiums	361,037	353,370	349,081
Net Investment Income	18,874	16,342	13,969
Claims and Claim Adjustment Expenses Incurred Related to Current Year	248,203	246,080	237,102
Claims and Claim Adjustment Expenses Incurred Related to Prior Years	40,105	7,608	(6,953)
Amortization of Deferred Policy Acquisition Costs	34,275	39,076	32,674
Paid Claims and Claims Adjustment Expenses	274,150	243,445	205,254
Premiums Written	$ 365,583	$ 361,829	$ 356,944