Derivative Financial Instruments (Cash Flow Hedge Derivative Gains and Losses Recognized in AOCI and Reclassified to Earnings) (Details) - Asset And Liability Management - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Foreign Exchange Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Net Gain/(Loss) Recognized in AOCI	$ 13.0	$ 8.9
Net Gain/(Loss) Reclassified from AOCI to Net Income
Net Gain/(Loss) Reclassified from AOCI to Net Income	16.6	5.0
Interest Rate Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Net Gain/(Loss) Recognized in AOCI	(1.4)	(0.2)
Net Gain/(Loss) Reclassified from AOCI to Net Income
Net Gain/(Loss) Reclassified from AOCI to Net Income	0.0	0.1
Net Gain/(Loss) Reclassified from AOCI to Net Income | Foreign Exchange Contracts
Net Gain/(Loss) Reclassified from AOCI to Net Income
Other Operating Income	2.4	0.7
Interest Income	14.2	4.4
Other Operating Expense	0.0	(0.1)
Net Gain/(Loss) Reclassified from AOCI to Net Income | Interest Rate Contracts
Net Gain/(Loss) Reclassified from AOCI to Net Income
Other Operating Income	0.0	0.0
Interest Income	0.0	0.1
Other Operating Expense	$ 0.0	$ 0.0