Schedule of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	$ 16.1	$ 166.4	$ 255.0
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	(52.5)	(130.3)	(97.0)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	(14.6)	(20.0)	8.4
Net Other Comprehensive Income (Loss)	(67.1)	(150.3)	(88.6)
Balance at End of Year	(51.0)	16.1	166.4
Net Unrealized Gain on Securities
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	204.3	290.3	135.7
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	226.5	(114.7)	154.3
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	9.8	28.7	0.3
Net Other Comprehensive Income (Loss)	236.3	(86.0)	154.6
Balance at End of Year	440.6	204.3	290.3
Net Gain on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	378.0	391.0	396.3
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	(15.8)	43.3	31.1
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	(34.7)	(56.3)	(36.4)
Net Other Comprehensive Income (Loss)	(50.5)	(13.0)	(5.3)
Balance at End of Year	327.5	378.0	391.0
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	(173.6)	(113.4)	(47.1)
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	(180.4)	(60.2)	(66.3)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	0.0	0.0	0.0
Net Other Comprehensive Income (Loss)	(180.4)	(60.2)	(66.3)
Balance at End of Year	(354.0)	(173.6)	(113.4)
Unrecognized Pension and Postretirement Benefit Costs
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	(392.6)	(401.5)	(229.9)
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	(82.8)	1.3	(216.1)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	10.3	7.6	44.5
Net Other Comprehensive Income (Loss)	(72.5)	8.9	(171.6)
Balance at End of Year	$ (465.1)	$ (392.6)	$ (401.5)