Schedule of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	$ (51.0)	$ 16.1	$ 166.4
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	205.6	(52.5)	(130.3)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	(27.1)	(14.6)	(20.0)
Net Other Comprehensive Income (Loss)	178.5	(67.1)	(150.3)
Balance at End of Year	127.5	(51.0)	16.1
Net Unrealized Gain on Securities
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	440.6	204.3	290.3
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	176.7	226.5	(114.7)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	(9.5)	9.8	28.7
Net Other Comprehensive Income (Loss)	167.2	236.3	(86.0)
Balance at End of Year	607.8	440.6	204.3
Net Gain on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	327.5	378.0	391.0
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	(14.7)	(15.8)	43.3
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	(30.5)	(34.7)	(56.3)
Net Other Comprehensive Income (Loss)	(45.2)	(50.5)	(13.0)
Balance at End of Year	282.3	327.5	378.0
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	(354.0)	(173.6)	(113.4)
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	99.5	(180.4)	(60.2)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	0.0	0.0	0.0
Net Other Comprehensive Income (Loss)	99.5	(180.4)	(60.2)
Balance at End of Year	(254.5)	(354.0)	(173.6)
Unrecognized Pension and Postretirement Benefit Costs
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Year	(465.1)	(392.6)	(401.5)
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	(55.9)	(82.8)	1.3
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	12.9	10.3	7.6
Net Other Comprehensive Income (Loss)	(43.0)	(72.5)	8.9
Balance at End of Year	$ (508.1)	$ (465.1)	$ (392.6)