Reserves for Unpaid Losses and Loss Adjustment Expenses (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended																12 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Loss and Loss Adjustment Expenses Incurred In 2012 Accident Year [Member]	Jun. 30, 2013 Loss and Loss Adjustment Expenses Incurred In 2011 Accident Year [Member]	Jun. 30, 2013 Loss and Loss Adjustment Expenses Incurred In 2010 Accident Year [Member]	Jun. 30, 2013 Loss and Loss Adjustment Expenses Incurred In 2009 And Prior Accident Year [Member]	Jun. 30, 2013 Personal Lines Business Unit [Member]	Jun. 30, 2012 Personal Lines Business Unit [Member]	Jun. 30, 2013 E & S Commercial Business Unit [Member]	Jun. 30, 2012 General Aviation Business Unit [Member]	Jun. 30, 2013 Standard Commercial Business Unit [Member]	Jun. 30, 2012 Standard Commercial Business Unit [Member]	Jun. 30, 2013 Standard Commercial Business Unit [Member] Loss Adjustment Expenses Recognized In 2010 [Member]	Jun. 30, 2013 Hallmark Select Business Unit [Member]	Jun. 30, 2013 Workers Compensation Risks [Member]	Jun. 30, 2012 Workers Compensation Risks [Member]	Dec. 31, 2012 Auto and Physical Damage [Member] E & S Commercial Business Unit [Member]	Jun. 30, 2012 Auto [Member] Personal Lines Business Unit [Member]	Jun. 30, 2012 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]
Favorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense				$ 1.4				$ 1.1				$ 2.7	$ 1.2	$ 1.9		$ 0.7	$ 1.0	$ 0.9
Unfavorable Adjustment to Prior Years Liability for Unpaid Claims and Claims Adjustment Expense	$ 5.4	$ 1.6	$ 7.4		$ 2.9	$ 3.2	$ 2.4		$ 1.0	$ 2.3	$ 9.3				$ 1.2				$ 1.8	$ 1.6	$ 0.7