ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Troubled Debt Restructuring (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended				12 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013		Dec. 31, 2013
Financing Receivable, Modifications [Line Items]
Commitments to lend additional funds to debtors owing receivables which were TDRs	$ 48				$ 48				$ 52
Net Change to ALLL Resulting from Modification	(1)		1		(11)		4
Charge-offs Resulting from Modification	4		4		11		13
Interest Rate Reduction
Financing Receivable, Modifications [Line Items]
Number of Contracts	591	[1]	882	[1]	2,008	[1]	2,751	[1]
Pre-Modification Outstanding Recorded Investment	9	[1]	21	[1]	38	[1]	65	[1]
Post-Modification Outstanding Recorded Investment	10	[1]	22	[1]	39	[1]	68	[1]
Maturity Extension
Financing Receivable, Modifications [Line Items]
Number of Contracts	104	[2]	33	[2]	408	[2]	201	[2]
Pre-Modification Outstanding Recorded Investment	9	[2]	2	[2]	29	[2]	13	[2]
Post-Modification Outstanding Recorded Investment	9	[2]	2	[2]	27	[2]	13	[2]
Other
Financing Receivable, Modifications [Line Items]
Number of Contracts	1,112	[3]	1,618	[3]	3,443	[3]	5,199	[3]
Pre-Modification Outstanding Recorded Investment	47	[3]	65	[3]	147	[3]	193	[3]
Post-Modification Outstanding Recorded Investment	43	[3]	60	[3]	137	[3]	180	[3]
Commercial
Financing Receivable, Modifications [Line Items]
Net Change to ALLL Resulting from Modification	0		1		(8)		1
Charge-offs Resulting from Modification	0		0		0		0
Commercial | Interest Rate Reduction
Financing Receivable, Modifications [Line Items]
Number of Contracts	5	[1]	29	[1]	20	[1]	100	[1]
Pre-Modification Outstanding Recorded Investment	0	[1]	1	[1]	7	[1]	5	[1]
Post-Modification Outstanding Recorded Investment	0	[1]	1	[1]	7	[1]	5	[1]
Commercial | Maturity Extension
Financing Receivable, Modifications [Line Items]
Number of Contracts	10	[2]	22	[2]	38	[2]	106	[2]
Pre-Modification Outstanding Recorded Investment	2	[2]	1	[2]	4	[2]	5	[2]
Post-Modification Outstanding Recorded Investment	2	[2]	1	[2]	4	[2]	5	[2]
Commercial | Other
Financing Receivable, Modifications [Line Items]
Number of Contracts	3	[3]	3	[3]	5	[3]	6	[3]
Pre-Modification Outstanding Recorded Investment	0	[3]	1	[3]	0	[3]	1	[3]
Post-Modification Outstanding Recorded Investment	0	[3]	1	[3]	0	[3]	1	[3]
Commercial real estate
Financing Receivable, Modifications [Line Items]
Net Change to ALLL Resulting from Modification	0		(2)		0		(3)
Charge-offs Resulting from Modification	0		0		0		0
Commercial real estate | Interest Rate Reduction
Financing Receivable, Modifications [Line Items]
Number of Contracts	1	[1]	6	[1]	3	[1]	10	[1]
Pre-Modification Outstanding Recorded Investment	0	[1]	4	[1]	0	[1]	7	[1]
Post-Modification Outstanding Recorded Investment	0	[1]	4	[1]	0	[1]	7	[1]
Commercial real estate | Maturity Extension
Financing Receivable, Modifications [Line Items]
Number of Contracts	3	[2]	0	[2]	5	[2]	1	[2]
Pre-Modification Outstanding Recorded Investment	1	[2]	0	[2]	1	[2]	0	[2]
Post-Modification Outstanding Recorded Investment	1	[2]	0	[2]	1	[2]	0	[2]
Commercial real estate | Other
Financing Receivable, Modifications [Line Items]
Number of Contracts	0	[3]	1	[3]	0	[3]	1	[3]
Pre-Modification Outstanding Recorded Investment	0	[3]	0	[3]	0	[3]	0	[3]
Post-Modification Outstanding Recorded Investment	0	[3]	0	[3]	0	[3]	0	[3]
Total commercial
Financing Receivable, Modifications [Line Items]
Net Change to ALLL Resulting from Modification	0		(1)		(8)		(2)
Charge-offs Resulting from Modification	0		0		0		0
Total commercial | Interest Rate Reduction
Financing Receivable, Modifications [Line Items]
Number of Contracts	6	[1]	35	[1]	23	[1]	110	[1]
Pre-Modification Outstanding Recorded Investment	0	[1]	5	[1]	7	[1]	12	[1]
Post-Modification Outstanding Recorded Investment	0	[1]	5	[1]	7	[1]	12	[1]
Total commercial | Maturity Extension
Financing Receivable, Modifications [Line Items]
Number of Contracts	13	[2]	22	[2]	43	[2]	107	[2]
Pre-Modification Outstanding Recorded Investment	3	[2]	1	[2]	5	[2]	5	[2]
Post-Modification Outstanding Recorded Investment	3	[2]	1	[2]	5	[2]	5	[2]
Total commercial | Other
Financing Receivable, Modifications [Line Items]
Number of Contracts	3	[3]	4	[3]	5	[3]	7	[3]
Pre-Modification Outstanding Recorded Investment	0	[3]	1	[3]	0	[3]	1	[3]
Post-Modification Outstanding Recorded Investment	0	[3]	1	[3]	0	[3]	1	[3]
Residential, including originated home equity products
Financing Receivable, Modifications [Line Items]
Net Change to ALLL Resulting from Modification	(1)		1		(4)		6
Charge-offs Resulting from Modification	2		1		7		7
Residential, including originated home equity products | Interest Rate Reduction
Financing Receivable, Modifications [Line Items]
Number of Contracts	57	[1]	102	[1]	193	[1]	340	[1]
Pre-Modification Outstanding Recorded Investment	6	[1]	11	[1]	20	[1]	38	[1]
Post-Modification Outstanding Recorded Investment	7	[1]	12	[1]	21	[1]	41	[1]
Residential, including originated home equity products | Maturity Extension
Financing Receivable, Modifications [Line Items]
Number of Contracts	87	[2]	11	[2]	353	[2]	91	[2]
Pre-Modification Outstanding Recorded Investment	6	[2]	1	[2]	24	[2]	8	[2]
Post-Modification Outstanding Recorded Investment	6	[2]	1	[2]	22	[2]	8	[2]
Residential, including originated home equity products | Other
Financing Receivable, Modifications [Line Items]
Number of Contracts	466	[3]	598	[3]	1,387	[3]	1,648	[3]
Pre-Modification Outstanding Recorded Investment	34	[3]	44	[3]	107	[3]	129	[3]
Post-Modification Outstanding Recorded Investment	32	[3]	42	[3]	101	[3]	122	[3]
Home equity products serviced by others
Financing Receivable, Modifications [Line Items]
Net Change to ALLL Resulting from Modification	(1)		1		(1)		1
Charge-offs Resulting from Modification	0		1		0		3
Home equity products serviced by others | Interest Rate Reduction
Financing Receivable, Modifications [Line Items]
Number of Contracts	8	[1]	4	[1]	29	[1]	23	[1]
Pre-Modification Outstanding Recorded Investment	0	[1]	1	[1]	1	[1]	2	[1]
Post-Modification Outstanding Recorded Investment	0	[1]	1	[1]	1	[1]	2	[1]
Home equity products serviced by others | Maturity Extension
Financing Receivable, Modifications [Line Items]
Number of Contracts	0	[2]	0	[2]	1	[2]	1	[2]
Pre-Modification Outstanding Recorded Investment	0	[2]	0	[2]	0	[2]	0	[2]
Post-Modification Outstanding Recorded Investment	0	[2]	0	[2]	0	[2]	0	[2]
Home equity products serviced by others | Other
Financing Receivable, Modifications [Line Items]
Number of Contracts	35	[3]	105	[3]	144	[3]	250	[3]
Pre-Modification Outstanding Recorded Investment	2	[3]	5	[3]	6	[3]	12	[3]
Post-Modification Outstanding Recorded Investment	2	[3]	4	[3]	6	[3]	9	[3]
Other secured retail
Financing Receivable, Modifications [Line Items]
Net Change to ALLL Resulting from Modification	0		0		0		0
Charge-offs Resulting from Modification	2		2		4		3
Other secured retail | Interest Rate Reduction
Financing Receivable, Modifications [Line Items]
Number of Contracts	7	[1]	29	[1]	65	[1]	224	[1]
Pre-Modification Outstanding Recorded Investment	0	[1]	0	[1]	1	[1]	2	[1]
Post-Modification Outstanding Recorded Investment	0	[1]	0	[1]	1	[1]	2	[1]
Other secured retail | Maturity Extension
Financing Receivable, Modifications [Line Items]
Number of Contracts	4	[2]	0	[2]	11	[2]	2	[2]
Pre-Modification Outstanding Recorded Investment	0	[2]	0	[2]	0	[2]	0	[2]
Post-Modification Outstanding Recorded Investment	0	[2]	0	[2]	0	[2]	0	[2]
Other secured retail | Other
Financing Receivable, Modifications [Line Items]
Number of Contracts	262	[3]	370	[3]	708	[3]	1,217	[3]
Pre-Modification Outstanding Recorded Investment	5	[3]	5	[3]	12	[3]	13	[3]
Post-Modification Outstanding Recorded Investment	3	[3]	3	[3]	8	[3]	10	[3]
Unsecured retail
Financing Receivable, Modifications [Line Items]
Net Change to ALLL Resulting from Modification	1		0		2		(1)
Charge-offs Resulting from Modification	0		0		0		0
Unsecured retail | Interest Rate Reduction
Financing Receivable, Modifications [Line Items]
Number of Contracts	513	[1]	712	[1]	1,698	[1]	2,054	[1]
Pre-Modification Outstanding Recorded Investment	3	[1]	4	[1]	9	[1]	11	[1]
Post-Modification Outstanding Recorded Investment	3	[1]	4	[1]	9	[1]	11	[1]
Unsecured retail | Maturity Extension
Financing Receivable, Modifications [Line Items]
Number of Contracts	0	[2]	0	[2]	0	[2]	0	[2]
Pre-Modification Outstanding Recorded Investment	0	[2]	0	[2]	0	[2]	0	[2]
Post-Modification Outstanding Recorded Investment	0	[2]	0	[2]	0	[2]	0	[2]
Unsecured retail | Other
Financing Receivable, Modifications [Line Items]
Number of Contracts	346	[3]	541	[3]	1,199	[3]	2,077	[3]
Pre-Modification Outstanding Recorded Investment	6	[3]	10	[3]	22	[3]	38	[3]
Post-Modification Outstanding Recorded Investment	6	[3]	10	[3]	22	[3]	38	[3]
Total retail
Financing Receivable, Modifications [Line Items]
Post-Modification Outstanding Recorded Investment									1,200	[2]
Net Change to ALLL Resulting from Modification	(1)		2		(3)		6
Charge-offs Resulting from Modification	4		4		11		13
Total retail | Interest Rate Reduction
Financing Receivable, Modifications [Line Items]
Number of Contracts	585	[1]	847	[1]	1,985	[1]	2,641	[1]
Pre-Modification Outstanding Recorded Investment	9	[1]	16	[1]	31	[1]	53	[1]
Post-Modification Outstanding Recorded Investment	10	[1]	17	[1]	32	[1]	56	[1]
Total retail | Maturity Extension
Financing Receivable, Modifications [Line Items]
Number of Contracts	91	[2]	11	[2]	365	[2]	94	[2]
Pre-Modification Outstanding Recorded Investment	6	[2]	1	[2]	24	[2]	8	[2]
Post-Modification Outstanding Recorded Investment	6	[2]	1	[2]	22	[2]	8	[2]
Total retail | Other
Financing Receivable, Modifications [Line Items]
Number of Contracts	1,109	[3]	1,614	[3]	3,438	[3]	5,192	[3]
Pre-Modification Outstanding Recorded Investment	47	[3]	64	[3]	147	[3]	192	[3]
Post-Modification Outstanding Recorded Investment	$ 43	[3]	$ 59	[3]	$ 137	[3]	$ 179	[3]

[1] Includes modifications that consist of multiple concessions, one of which is an interest rate reduction.

[2] Includes modifications that consist of multiple concessions, one of which is a maturity extension (unless one of the other concessions was an interest rate reduction).

[3] Includes modifications other than interest rate reductions or maturity extensions, such as lowering scheduled payments for a specified period of time, principal forbearance, capitalizing arrearages, and principal forgiveness. Also included are the following: deferrals, trial modifications, certain bankruptcies, loans in forbearance and prepayment plans. Modifications can include the deferral of accrued interest resulting in post modification balances being higher than pre-modification.