Reserves for Unpaid Losses and Loss Adjustment Expenses (Details Textual) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Favorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense	$ 3.7
Unfavorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense		16.4	9.2
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense, Amount	3.7	16.4	9.2
Loss Adjustment Expenses Recognized in 2011 [Member]
Favorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense	0.4
Loss Adjustment Expenses Recognized in 2010 [Member]
Favorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense	0.8
Unfavorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense		15.0
Loss Adjustment Expenses Recognized in 2009 [Member]
Favorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense	2.5
Unfavorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense		3.6	5.4
Loss Adjustment Expenses Recognized in 2008 [Member]
Favorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense		2.2
Unfavorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense			0.6
Loss Adjustment Expenses Recognized in 2007 [Member]
Unfavorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense			3.2
Personal Lines Business Unit [Member]
Unfavorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense	3.6
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense, Amount		19.6	3.1
E&S Commercial [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense, Amount	(0.3)	3.7	1.6
General Aviation Business Unit [Member]
Favorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense		6.1
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense, Amount	(3.3)		(0.2)
Standard Commercial Segment [Member]
Favorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense		0.8
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense, Amount	(3.7)		4.6
Excess and Umbrella Business Unit [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense, Amount			0.1
Florida Personal Lines Claims [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense, Amount		$ 10.3