Accumulated Other Comprehensive Income (Loss) (Summary of Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance			$ 8,705.9
Net Change	$ (20.1)	$ 0.0	113.0	$ 46.0
Ending balance	9,579.8	8,784.5	9,579.8	8,784.5
Net Unrealized Gains (Losses) on Securities Available for Sale
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance			(31.0)	27.6
Net Change	(13.9)	(7.0)	94.3	24.7
Ending balance	63.3	52.3	63.3	52.3
Net Unrealized Gains (Losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance			(3.0)	(4.7)
Net Change	0.1	3.2	6.6	5.3
Ending balance	3.6	0.6	3.6	0.6
Net Foreign Currency Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance			(17.6)	(1.7)
Net Change	(9.5)	(2.3)	0.7	(2.4)
Ending balance	(16.9)	(4.1)	(16.9)	(4.1)
Net Pension and Other Postretirement Benefit Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance			(321.1)	(340.9)
Net Change	3.3	6.1	11.4	18.4
Ending balance	(309.7)	(322.5)	(309.7)	(322.5)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance			(372.7)	(319.7)
Net Change				46.0
Ending balance	$ (259.7)	$ (273.7)	$ (259.7)	$ (273.7)