DIVESTITURES AND BRANCH ASSETS AND LIABILITIES HELD FOR SALE - Narrative (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended	12 Months Ended
	Jun. 20, 2014 branch	Dec. 31, 2014	Dec. 31, 2013
Disposal of Branch Assets and Liabilities [Abstract]
Deposit liabilities			$ 5,277
Loans (primarily middle market, small business, home equity and credit card balances)			1,078
Disposed of by sale | Illinois | Retail branches
Disposal of Branch Assets and Liabilities [Abstract]
Number of branches sold	103
Deposit liabilities	4,800
Loans (primarily middle market, small business, home equity and credit card balances)	1,000
Gain (loss) on sale	288
Disposed of by sale | Illinois | Retail branches | Deposits
Disposal of Branch Assets and Liabilities [Abstract]
Gain (loss) on sale	286
Interest expense on deposits		4
Disposed of by sale | Illinois | Retail branches | Loans
Disposal of Branch Assets and Liabilities [Abstract]
Gain (loss) on sale	11
Interest and fee income on loans		20
Disposed of by sale | Illinois | Retail branches | Other branch assets
Disposal of Branch Assets and Liabilities [Abstract]
Gain (loss) on sale	$ (9)