Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Consolidated Statements of Comprehensive Income [Abstract]
Net Income	$ 85.7	$ 114.5	$ 217.7
Unrealized Holding Gains (Losses)	(177.3)	234.6	(362.8)
Foreign Currency Translation Adjustments	(1.4)	(1.0)	0.2
Decrease (Increase) in Net Unrecognized Postretirement Benefit Costs	26.1	(98.5)	86.6
Other Comprehensive Income (Loss) Before Income Taxes	(152.6)	135.1	(276.0)
Other Comprehensive Income Tax Benefit (Expense)	54.2	(47.7)	98.6
Other Comprehensive Income (Loss)	(98.4)	87.4	(177.4)
Total Comprehensive Income (Loss)	$ (12.7)	$ 201.9	$ 40.3