Schedule of Accumulated Other Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss), Net of Tax
Balance, Beginning of Period	$ 255.0	$ 628.0
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	(97.0)	(382.6)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	8.4	9.6
Total Other Comprehensive Income (Loss)	(88.6)	(373.0)	166.2
Balance, End of Period	166.4	255.0	628.0
Net Unrealized Gain on Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax
Balance, Beginning of Period	135.7	873.5
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	154.3	(746.4)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	0.3	8.6
Total Other Comprehensive Income (Loss)	154.6	(737.8)
Balance, End of Period	290.3	135.7
Net Gain on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax
Balance, Beginning of Period	396.3	401.6
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	31.1	9.7
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	(36.4)	(15.0)
Total Other Comprehensive Income (Loss)	(5.3)	(5.3)
Balance, End of Period	391.0	396.3
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax
Balance, Beginning of Period	(47.1)	(72.6)
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	(66.3)	25.5
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	0	0
Total Other Comprehensive Income (Loss)	(66.3)	25.5
Balance, End of Period	(113.4)	(47.1)
Unrecognized Pension and Postretirement Benefit Costs
Accumulated Other Comprehensive Income (Loss), Net of Tax
Balance, Beginning of Period	(229.9)	(574.5)
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	(216.1)	328.6
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	44.5	16.0
Total Other Comprehensive Income (Loss)	(171.6)	344.6
Balance, End of Period	$ (401.5)	$ (229.9)