Schedule VI. Supplemental Information Concerning Property and Casualty Insurance Operations (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Net Realized Investment Gains	$ 7,270		$ 8,695		$ 5,453
Claims and Claim Adjustment Expenses Incurred Related to: Current Year	566,555		494,841		512,564
Claims and Claim Adjustment Expenses Incurred Related to: Prior Years	(56,744)		(57,487)		(73,427)
Amortization of the value of business acquired asset	0		0		1,673
Mercer Insurance Group [Member]
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Amortization of the value of business acquired asset					1,673
Consolidated property and casualty insurance entity
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Deferred Policy Acquisition Costs	72,861		67,663		64,947
Reserves for Unpaid Claims and Claim Adjustment Expenses	969,437		960,651		971,911
Unearned Premiums	378,635		340,387		311,561
Earned Premiums	766,939		694,192		629,411
Net Realized Investment Gains	4,177		6,260		1,676
Net Investment Income	44,236		46,332		41,879
Claims and Claim Adjustment Expenses Incurred Related to: Current Year	566,555		494,841		512,564
Claims and Claim Adjustment Expenses Incurred Related to: Prior Years	(56,744)		(57,487)		(73,427)
Amortization of Deferred Policy Acquisition Costs	161,310	[1]	147,175	[1]	134,444	[1]
Paid Claims and Claim Adjustment Expenses	489,631		419,894		395,788
Premiums Written	$ 804,715		$ 722,821		$ 655,331

[1] 2012 includes amortization of the value of business acquired asset that was recorded as a result of our acquisition of Mercer Insurance Group, Inc. totaling $1,673.