INVESTMENT SECURITIES (Securities Pledged as Collateral) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Financial Instruments Owned and Pledged as Collateral [Line Items]
Securities pledged as collateral, fair value	$ 3,500.0	$ 3,600.0
Public fund deposits [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Securities pledged as collateral, fair value	2,600.0	2,600.0
Repurchase agreements, hedging activities and recourse on loan sales [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Securities pledged as collateral, fair value	361.2	445.9
Overnight customer deposits [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Securities pledged as collateral, fair value	$ 512.4	$ 562.3