BORROWED FUNDS - Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Short-term borrowed funds	$ 10,546	$ 10,529
Federal Home Loan Bank Advances and Letters of Credit [Member] | Secured Debt
Debt Instrument [Line Items]
Short-term borrowed funds	11,500	11,300
Federal Home Loan advances
Debt Instrument [Line Items]
Available borrowing capacity	3,300	$ 3,500
Federal Reserve Bank Advances
Debt Instrument [Line Items]
Available borrowing capacity	$ 27,900