Allowance for Credit Losses (Changes in Allowance for Credit Losses) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	$ 233.3	$ 295.9
Charge-Offs	(5.3)	(7.5)
Recoveries	2.6	2.9
Net (Charge-Offs) Recoveries	(2.7)	(4.6)
Provision for Credit Losses	2.0	(4.5)
Effect of Foreign Exchange Rates	0.0	(0.1)
Balance at end of period	232.6	286.7
Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	114.8	169.7
Charge-Offs	(3.5)	(2.7)
Recoveries	1.2	1.7
Net (Charge-Offs) Recoveries	(2.3)	(1.0)
Provision for Credit Losses	2.7	(4.3)
Effect of Foreign Exchange Rates	0.0	(0.1)
Balance at end of period	115.2	164.3
Personal
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	118.5	126.2
Charge-Offs	(1.8)	(4.8)
Recoveries	1.4	1.2
Net (Charge-Offs) Recoveries	(0.4)	(3.6)
Provision for Credit Losses	(0.7)	(0.2)
Effect of Foreign Exchange Rates	0.0	0.0
Balance at end of period	$ 117.4	$ 122.4