Derivative Instruments (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended		3 Months Ended	9 Months Ended						3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2012 Derivatives designated as hedging instruments	Sep. 30, 2013 Derivatives designated as hedging instruments	Sep. 30, 2012 Derivatives designated as hedging instruments	Sep. 30, 2012 Derivatives designated as hedging instruments Fair Value Hedge Interest Rate Swaps Interest expense	Sep. 30, 2013 Derivatives designated as hedging instruments Fair Value Hedge Interest Rate Swaps Interest expense	Sep. 30, 2012 Derivatives designated as hedging instruments Fair Value Hedge Interest Rate Swaps Interest expense	Sep. 30, 2013 Derivatives designated as hedging instruments Cash Flow Hedge Interest income	Sep. 30, 2012 Derivatives designated as hedging instruments Cash Flow Hedge Interest income	Sep. 30, 2013 Derivatives designated as hedging instruments Cash Flow Hedge Interest Rate Swaps Interest income	Sep. 30, 2012 Derivatives designated as hedging instruments Cash Flow Hedge Interest Rate Swaps Interest income	Sep. 30, 2013 Derivatives not designated as hedging instruments	Sep. 30, 2012 Derivatives not designated as hedging instruments	Sep. 30, 2013 Derivatives not designated as hedging instruments	Sep. 30, 2012 Derivatives not designated as hedging instruments	Sep. 30, 2013 Derivatives not designated as hedging instruments Interest Rate Contracts Other noninterest income	Sep. 30, 2012 Derivatives not designated as hedging instruments Interest Rate Contracts Other noninterest income	Sep. 30, 2013 Derivatives not designated as hedging instruments Interest Rate Contracts Other noninterest income	Sep. 30, 2012 Derivatives not designated as hedging instruments Interest Rate Contracts Other noninterest income	Sep. 30, 2013 Derivatives not designated as hedging instruments Option contracts Other noninterest income	Sep. 30, 2012 Derivatives not designated as hedging instruments Option contracts Other noninterest income	Sep. 30, 2013 Derivatives not designated as hedging instruments Option contracts Other noninterest income	Sep. 30, 2012 Derivatives not designated as hedging instruments Option contracts Other noninterest income	Sep. 30, 2013 Derivatives not designated as hedging instruments Foreign Exchange Contracts International services income	Sep. 30, 2012 Derivatives not designated as hedging instruments Foreign Exchange Contracts International services income	Sep. 30, 2013 Derivatives not designated as hedging instruments Foreign Exchange Contracts International services income	Sep. 30, 2012 Derivatives not designated as hedging instruments Foreign Exchange Contracts International services income	Sep. 30, 2013 Derivatives designated and not designated as hedging instruments	Sep. 30, 2013 Derivatives designated and not designated as hedging instruments Interest Rate Swaps	Dec. 31, 2012 Derivatives designated and not designated as hedging instruments Interest Rate Swaps
Derivative instruments gain (loss)
Derivative Instruments, Gain (Loss) Recognized in Income, Net	$ 2.1	$ 1.1	$ 6.3	$ (2.1)	$ (1.0)	$ (6.2)			$ 0.1	$ 0.1	$ 6.8	$ 6.1	$ 21.6	$ 17.1	$ (0.3)	$ 0.1	$ 0.9	$ (0.5)	$ (0.1)	$ (0.3)	$ 0.3	$ (1.0)	$ 7.2	$ 6.3	$ 20.4	$ 18.6
Amount of gains reclassified from AOCI to Interest							0.1	0.1
Credit Risk Exposure and Collateral
Aggregate fair value of derivatives with credit-risk-related contingent features, net liability position																											11.5
Collateral delivered on swap agreements in the form of securities, with credit-risk-related contingent features																											1.2
Collateral delivered on swap agreements in the form of cash, with credit-risk-related contingent features																											10.7
Interest rate swap credit risk exposure																												0.6	1.6
Collateral received from swap counterparties																												0	1.0
Collateral delivered on swap agreements, without credit-risk contingent features																												$ 12.4