Business Combinations (Details Textual) (USD $)	9 Months Ended		12 Months Ended		12 Months Ended
	Sep. 30, 2012	Aug. 29, 2008 Excess and Umbrella Business Unit [Member]	Dec. 31, 2010 State Auto Financial Corporation Inc [Member]	Jan. 03, 2011 State Auto Financial Corporation Inc [Member]	Dec. 31, 2010 Hallmark National Insurance Company [Member]	Dec. 31, 2011 TBIC Holding Corporation [Member]	Jul. 02, 2011 TBIC Holding Corporation [Member]
Noncontrolling Interest, Ownership Percentage by Parent		80.00%
Percentage Of Ownership Interests Authorized For Purchase	20.00%	20.00%
Redemption Value Of Call and Put Option	$ 1,700,000
Business Acquisition, Cost of Acquired Entity, Cash Paid				14,000,000			1,600,000
Business Acquisition Cost Of Acquired Entity Purchase Price Additional Amout			2,000,000			350,000
Gross Collected Premium Percentage					2.00%
Business Acquisition, Contingent Consideration, at Fair Value							3,000,000
Business Acquisition, Cost of Acquired Entity, Purchase Price		15,000,000
Business Combination, Bargain Purchase, Gain Recognized, Amount						165,000
Holdback Purchase Price Estimated To Pay	350,000
Accounts Payable and Other Accrued Liabilities	$ 1,700,000