Discontinued Operations (Loss from Discontinued Operations) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues
Earned insurance premiums									$ 1,987.3	$ 2,063.6	$ 1,924.5
Net investment income									110.9	153.6	184.5
Net realized and unrealized investment gains									161.7	118.2	74.1
Other revenue									57.5	100.3	(10.0)
Revenues (including realized gains and losses)	626.6	574.1	489.3	627.4	566.4	697.4	542.3	629.7	2,317.4	2,435.7	2,173.1
Expenses
Loss and loss adjustment expenses									1,040.5	1,193.9	1,174.3
Insurance and reinsurance acquisition expenses									376.9	430.2	402.2
Other underwriting expenses									331.3	321.8	268.1
General and administrative expenses									181.3	182.2	175.3
Total expenses	492.4	518.8	485.7	475.6	617.2	562.3	504.7	488.8	1,972.5	2,172.9	2,075.1
Net loss from discontinued operations, net of tax	(0.3)	0.4	3.9	0.5	0.5	(106.8)	0.5	(9.2)	(42.1)	(24.0)	(36.7)
Gain (loss) on sale of discontinued operations, net of tax									46.6	(91.0)	658.3
Discontinued Operations
Revenues
Earned insurance premiums									0.8	10.6	731.2
Net investment income									0	0	12.0
Net realized and unrealized investment gains									0	0	0.7
Other revenue									10.8	0	55.1
Revenues (including realized gains and losses)									11.6	10.6	799.0
Expenses
Loss and loss adjustment expenses									78.9	48.4	574.9
Insurance and reinsurance acquisition expenses									0	(2.1)	157.0
Other underwriting expenses									(0.2)	1.7	91.4
General and administrative expenses									0	0	38.3
Total expenses									78.7	48.0	861.6
Loss from discontinued operations									(67.1)	(37.4)	(62.6)
Income tax benefit									(25.0)	(13.4)	(25.9)
Net loss from discontinued operations, net of tax									(42.1)	(24.0)	(36.7)
Gain (loss) on sale of discontinued operations, net of tax									46.6	(91.0)	658.3
Net income (loss) from discontinued operations									$ 4.5	$ (115.0)	$ 621.6