Reserves for Unpaid Losses and Loss Adjustment Expenses (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Favorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense		$ 2.2		$ 3.6
Unfavorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense	0.5		8.0
Loss and Loss Adjustment Expenses Incurred In 2012 Accident Year [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Unfavorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense			5.0
Loss and Loss Adjustment Expenses Incurred In 2011 Accident Year [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Unfavorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense			2.4
Loss and Loss Adjustment Expenses Incurred In 2010 Accident Year [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Unfavorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense			1.6
Loss and Loss Adjustment Expenses Incurred In 2009 And Prior Accident Year [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Favorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense			1.0
Personal Lines Business Unit [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Unfavorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense			1.5	2.9
E & S Commercial Business Unit [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Favorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense				1.1
Unfavorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense			11.7
Standard Commercial Business Unit [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Favorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense			2.4
Standard Commercial Business Unit [Member] | Loss Adjustment Expenses Recognized In 2010 [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Favorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense			2.4
Hallmark Select Business Unit [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Favorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense			1.6	2.6
Workers Compensation Risks [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Favorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense			1.2	0.8
Commercial Auto Liability [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Favorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense				2.0
Auto [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Unfavorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense				2.2
Low Value Dwelling/Homeowners [Member] | Personal Lines Business Unit [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Unfavorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense				$ 0.7