Discontinued Operations (Summary of the Results of Operations) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended					12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 Segment, Discontinued Operations	Mar. 31, 2013 Segment, Discontinued Operations	Mar. 31, 2014 Runoff Segment, Discontinued Operations	Dec. 31, 2013 Runoff Segment, Discontinued Operations
Discontinued Operations
Net written premiums	$ 311.1	$ 265.1	$ (0.1)	$ 0.8
Revenues
Earned premiums	276.5	286.5	(0.1)	0.9
Total revenues	306.4	348.3	(0.1)	0.9
Expenses
Loss and loss adjustment expenses	149.4	148.9	0	0
Policy acquisition expenses			0	0.1
Other underwriting expenses	46.7	54.8	0.7	0.1
Total expenses	252.0	260.2	0.7	0.2
Pre-tax income (loss)			(0.8)	0.7	69.0	69.0
Income tax benefit (expense)	6.5	19.8	0.3	(0.2)
Income (loss) from discontinued operations, net of tax			$ (0.5)	$ 0.5