FAIR VALUE MEASUREMENT - Estimate Fair Value of Financial Instruments Not Carried at Fair Value (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Assets
Loans	$ 6,575,000,000	$ 5,901,000,000
Liabilities
Deposits	899,647,000,000	899,332,000,000
Allowance for loan losses	14,598,000,000	15,994,000,000	18,923,000,000	19,648,000,000
Lease finance receivables	2,600,000,000	2,700,000,000
Corporate
Assets
Loans	6,537,000,000	5,858,000,000
Carrying value
Assets
Investments	29,000,000,000	30,500,000,000
Federal funds sold and securities borrowed or purchased under agreements to resell	103,100,000,000	98,400,000,000
Loans	597,300,000,000	620,000,000,000
Other financial assets	219,000,000,000	213,800,000,000
Liabilities
Deposits	898,000,000,000	897,600,000,000
Federal funds purchased and securities loaned or sold under agreements to repurchase, selected portfolios of securities sold under agreements to repurchase and securities loaned	141,100,000,000	136,700,000,000
Long-term debt	185,100,000,000	196,900,000,000
Other financial liabilities	125,600,000,000	136,200,000,000
Fair value
Assets
Investments	30,700,000,000	32,200,000,000
Federal funds sold and securities borrowed or purchased under agreements to resell	103,100,000,000	98,400,000,000
Loans	597,100,000,000	617,600,000,000
Other financial assets	219,000,000,000	213,800,000,000
Liabilities
Deposits	890,300,000,000	894,400,000,000
Federal funds purchased and securities loaned or sold under agreements to repurchase, selected portfolios of securities sold under agreements to repurchase and securities loaned	141,100,000,000	136,700,000,000
Long-term debt	192,000,000,000	202,500,000,000
Other financial liabilities	125,600,000,000	136,200,000,000
Fair value | Level 1
Assets
Investments	4,300,000,000	4,500,000,000
Federal funds sold and securities borrowed or purchased under agreements to resell	0	0
Loans	0	0
Other financial assets	8,100,000,000	8,300,000,000
Liabilities
Deposits	0	0
Federal funds purchased and securities loaned or sold under agreements to repurchase, selected portfolios of securities sold under agreements to repurchase and securities loaned	0	0
Long-term debt	0	0
Other financial liabilities	0	0
Fair value | Level 2
Assets
Investments	23,800,000,000	25,200,000,000
Federal funds sold and securities borrowed or purchased under agreements to resell	96,000,000,000	89,700,000,000
Loans	6,100,000,000	5,600,000,000
Other financial assets	147,700,000,000	151,900,000,000
Liabilities
Deposits	735,300,000,000	766,700,000,000
Federal funds purchased and securities loaned or sold under agreements to repurchase, selected portfolios of securities sold under agreements to repurchase and securities loaned	140,900,000,000	136,500,000,000
Long-term debt	169,800,000,000	172,700,000,000
Other financial liabilities	31,700,000,000	41,400,000,000
Fair value | Level 3
Assets
Investments	2,600,000,000	2,500,000,000
Federal funds sold and securities borrowed or purchased under agreements to resell	7,100,000,000	8,700,000,000
Loans	591,000,000,000	612,000,000,000
Other financial assets	63,200,000,000	53,600,000,000
Liabilities
Deposits	155,000,000,000	127,700,000,000
Federal funds purchased and securities loaned or sold under agreements to repurchase, selected portfolios of securities sold under agreements to repurchase and securities loaned	200,000,000	200,000,000
Long-term debt	22,200,000,000	29,800,000,000
Other financial liabilities	93,900,000,000	94,800,000,000
Fair value | Level 3 | Corporate
Fair value measurements additional disclosures
Unfunded lending commitments	$ 4,600,000,000	$ 5,500,000,000