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Investment Securities (Investment gains (losses) for Level 3) (Details) (Level 3 Inputs, USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Fixed maturity investments.	Jun. 30, 2013 Fixed maturity investments.	Jun. 30, 2014 Fixed maturity investments.	Jun. 30, 2013 Fixed maturity investments.	Jun. 30, 2014 Common equity securities	Jun. 30, 2013 Common equity securities	Jun. 30, 2014 Common equity securities	Jun. 30, 2013 Common equity securities	Jun. 30, 2014 Convertible Debt Securities	Dec. 31, 2011 Convertible Debt Securities	Jun. 30, 2014 Convertible Debt Securities	Jun. 30, 2013 Convertible Debt Securities	Jun. 30, 2014 Other long-term investments	Jun. 30, 2013 Other long-term investments	Jun. 30, 2014 Other long-term investments	Jun. 30, 2013 Other long-term investments
Schedule of Trading Securities and Other Trading Assets [Line Items]
Unrealized gains (losses) on investments	$ 14.3	$ 1.8	$ 21.4	$ 8.3	$ 0.2	$ (0.4)	$ 0.4	$ (0.2)	$ 2.0	$ 0.8	$ 2.8	$ 0.7	$ 3.2	$ 0	$ 3.2	$ 0	$ 8.9	$ 1.4	$ 15.0	$ 7.8

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- Definition

The aggregate increase (decrease) in the market value of unsold investments whose gains (losses) are included in earnings.

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No definition available.

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