Loss and Loss Adjustment Expense Reserves (Loss and Loss Adjustment Expense) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Equity in earnings of unconsolidated affiliates, net of tax	$ 0.0	$ 6.8	$ 0.0	$ 14.1
Gross beginning balance	1,343.8	1,304.0	1,389.8	1,342.2	$ 1,342.2
Less beginning reinsurance recoverable on unpaid losses	(150.4)	(141.6)	(186.0)	(161.6)	(161.6)
Net loss and LAE reserves	1,193.4	1,162.4	1,203.8	1,180.6	1,180.6
Loss and LAE incurred relating to current year losses	166.7	196.5	327.9	366.3
Net (favorable) and unfavorable loss reserve development	15.3	(0.3)	15.2	(2.2)
Total incurred losses and LAE	182.0	196.2	343.1	364.1
Current year losses	(38.1)	(43.9)	(61.2)	(67.2)
Prior year losses	(123.5)	(111.4)	(272.1)	(275.4)
Total loss and LAE payments	(161.6)	(155.3)	(333.3)	(342.6)
Net ending balance	1,213.8	1,203.7	1,213.8	1,203.7	1,203.8
Plus ending reinsurance recoverable on unpaid losses	162.8	147.1	162.8	147.1	186.0
Gross ending balance	1,376.6	1,350.8	1,376.6	1,350.8	$ 1,389.8
Star & Shield Insurance Exchange
Net ending balance	5.3	6.1	5.3	6.1
Star & Shield Insurance Exchange
Liability for Unpaid Claims and Claims Adjustment Expense, Consolidated Claims Current Year	5.3	6.5	5.5	7.7
Net (favorable) and unfavorable loss reserve development	$ (0.1)	$ (0.3)	$ (0.2)	$ (0.4)