Income Taxes - Comprehensive Income Tax Benefit and Expense (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax Expense (Benefit) [Abstract]
Income Tax Expense	$ 4.3	$ (25.9)	$ 5.1	$ (14.1)	$ (6.1)	$ 6.1	$ 11.5	$ (18.1)	$ (30.6)	$ (6.6)	$ (63.8)
Income Tax Expense - Discontinued Operations	(2.1)	0.1	(0.3)	(5.0)	(0.9)	0.3	(3.2)	(2.9)	(7.3)	(6.7)	(10.3)
Equity in:
Equity in Net Loss of Former Investee									0	0	0.1
Equity in Other Comprehensive (Income) Loss of Former Investee									0	0	(1.0)
Unrealized Appreciation on Securities									(34.4)	(71.6)	(62.6)
Foreign Currency Translation Adjustments on Investments									(0.6)	(0.1)	0.2
Tax Effects from Postretirement Benefit Plans									4.6	15.9	9.3
Tax Effects from Long-Term Equity-based Compensation included in Pain-in Capital									(0.1)	(1.0)	(2.0)
Comprehensive Income Tax Expense									$ 68.4	$ 70.1	$ 130.1