Discontinued Operations (Net Assets Held for Sale) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012
Assets held for sale
Fixed maturity investments, at fair value	$ 5,008.0		$ 5,030.5
Reinsurance recoverable on unpaid losses	433.2		428.1
Reinsurance recoverable on paid losses	18.9		25.4
Insurance and reinsurance premiums receivable	717.9		518.9
Deferred tax asset	462.8		512.1
Other assets	520.1		458.1
Total assets	12,357.9		12,144.3
Liabilities held for sale
Loss and loss adjustment expense reserves	3,053.3	3,048.4	3,079.3	3,057.9	3,100.6	3,168.9
Unearned insurance premiums	1,093.4		901.4
Ceded reinsurance payable	159.2		71.9
Other liabilities	336.8		362.9
Total liabilities	7,749.3		7,746.9
Segment, Discontinued Operations
Assets held for sale
Fixed maturity investments, at fair value	203.8		236.3
Reinsurance recoverable on unpaid losses	1,507.4		1,604.7
Reinsurance recoverable on paid losses	7.9		10.7
Insurance and reinsurance premiums receivable	13.2		9.1
Deferred tax asset	2.8		3.3
Other assets	15.6		16.0
Total assets	1,750.7		1,880.1
Liabilities held for sale
Loss and loss adjustment expense reserves	1,666.3		1,793.1
Unearned insurance premiums	0.3		0.2
Ceded reinsurance payable	11.9		12.3
Other liabilities	72.2		74.5
Total liabilities	1,750.7		1,880.1
Net assets held for sale	$ 0		$ 0