Accumulated Other Comprehensive Income (Loss) (Summary of Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance			$ 8,705.9
Net Change	$ 44.3	$ (7.3)	133.1	$ 46.0
Ending balance	8,951.5	8,749.3	8,951.5	8,749.3
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	33.5	(22.4)	108.2	31.7
Ending balance	77.2	59.3	77.2	59.3
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	0.5	3.2	6.6	2.1
Ending balance	3.6	(2.6)	3.6	(2.6)
Net Foreign Currency Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance			(17.6)	(1.7)
Net Change	6.3	5.8	10.2	(0.1)
Ending balance	(7.4)	(1.8)	(7.4)	(1.8)
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	4.0	6.1	8.1	12.3
Ending balance	(313.0)	(328.6)	(313.0)	(328.6)
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance			(372.7)	(319.7)
Net Change			133.1	46.0
Ending balance	$ (239.6)	$ (273.7)	$ (239.6)	$ (273.7)