Schedule of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income, Net of Tax
Balance at Beginning of Period	$ 104.9	$ 339.8	$ (51.0)	$ 16.1
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	27.3	117.7	197.4	443.7
Reclassification from Accumulated Other Comprehensive Income or Loss	(7.9)	(6.8)	(22.1)	(9.1)
Total Other Comprehensive Income	19.4	110.9	175.3	434.6
Balance at End of Period	124.3	450.7	124.3	450.7
Net Unrealized Gain on Securities
Accumulated Other Comprehensive Income, Net of Tax
Balance at Beginning of Period	558.2	661.1	440.6	204.3
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	4.4	143.0	125.7	588.9
Reclassification from Accumulated Other Comprehensive Income or Loss	(5.2)	(0.9)	(8.9)	10.0
Total Other Comprehensive Income	(0.8)	142.1	116.8	598.9
Balance at End of Period	557.4	803.2	557.4	803.2
Net Gain on Cash Flow Hedges
Accumulated Other Comprehensive Income, Net of Tax
Balance at Beginning of Period	304.5	343.6	327.5	378.0
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	(7.9)	0.1	(14.0)	(16.0)
Reclassification from Accumulated Other Comprehensive Income or Loss	(5.9)	(8.5)	(22.8)	(26.8)
Total Other Comprehensive Income	(13.8)	(8.4)	(36.8)	(42.8)
Balance at End of Period	290.7	335.2	290.7	335.2
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income, Net of Tax
Balance at Beginning of Period	(297.1)	(279.4)	(354.0)	(173.6)
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	31.8	(25.8)	88.7	(131.6)
Reclassification from Accumulated Other Comprehensive Income or Loss	0.0	0.0	0.0	0.0
Total Other Comprehensive Income	31.8	(25.8)	88.7	(131.6)
Balance at End of Period	(265.3)	(305.2)	(265.3)	(305.2)
Unrecognized Pension and Postretirement Benefit Costs
Accumulated Other Comprehensive Income, Net of Tax
Balance at Beginning of Period	(460.7)	(385.5)	(465.1)	(392.6)
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	(1.0)	0.4	(3.0)	2.4
Reclassification from Accumulated Other Comprehensive Income or Loss	3.2	2.6	9.6	7.7
Total Other Comprehensive Income	2.2	3.0	6.6	10.1
Balance at End of Period	$ (458.5)	$ (382.5)	$ (458.5)	$ (382.5)