Schedule VI. Supplemental Information Concerning Property and Casualty Insurance Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Net Realized Investment Gains	$ 6,103	$ 2,846	$ 7,270
Claims and Claim Adjustment Expenses Incurred Related to: Current Year	683,662	560,482	566,555
Claims and Claim Adjustment Expenses Incurred Related to: Prior Years	(31,229)	(40,395)	(56,744)
Consolidated Property and Casualty Insurance Entity
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Deferred Policy Acquisition Costs	93,362	90,547	72,861
Reserves for Unpaid Claims and Claim Adjustment Expenses	1,123,896	1,003,895	969,437
Unearned Premiums	443,802	414,971	378,635
Earned Premiums	936,131	851,695	766,939
Net Realized Investment Gains	4,947	1,124	4,177
Net Investment Income	55,284	46,559	44,236
Claims and Claim Adjustment Expenses Incurred Related to: Current Year	683,662	560,482	566,555
Claims and Claim Adjustment Expenses Incurred Related to: Prior Years	(31,229)	(40,395)	(56,744)
Amortization of Deferred Policy Acquisition Costs	202,892	180,183	161,310
Paid Claims and Claim Adjustment Expenses	537,573	476,525	489,631
Premiums Written	$ 964,970	$ 887,874	$ 804,715