Schedule of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	$ 166.4	$ 255.0	$ 628.0
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	(130.3)	(97.0)	(382.6)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	(20.0)	8.4	9.6
Net Other Comprehensive Income (Loss)	(150.3)	(88.6)	(373.0)
Balance at End of Year	16.1	166.4	255.0
Net Unrealized Gain on Securities
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	290.3	135.7	873.5
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	(114.7)	154.3	(746.4)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	28.7	0.3	8.6
Net Other Comprehensive Income (Loss)	(86.0)	154.6	(737.8)
Balance at End of Year	204.3	290.3	135.7
Net Gain on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	391.0	396.3	401.6
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	43.3	31.1	9.7
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	(56.3)	(36.4)	(15.0)
Net Other Comprehensive Income (Loss)	(13.0)	(5.3)	(5.3)
Balance at End of Year	378.0	391.0	396.3
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	(113.4)	(47.1)	(72.6)
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	(60.2)	(66.3)	25.5
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	0.0	0.0	0.0
Net Other Comprehensive Income (Loss)	(60.2)	(66.3)	25.5
Balance at End of Year	(173.6)	(113.4)	(47.1)
Unrecognized Pension and Postretirement Benefit Costs
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	(401.5)	(229.9)	(574.5)
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	1.3	(216.1)	328.6
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	7.6	44.5	16.0
Net Other Comprehensive Income (Loss)	8.9	(171.6)	344.6
Balance at End of Year	$ (392.6)	$ (401.5)	$ (229.9)