ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Impaired Loans by Class (Details) - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance		$ 609	$ 789
Allowance on Impaired Loans		127	129
Impaired Loans Without a Related Allowance		755	624
Unpaid Contractual Balance		1,667	1,727
Total Recorded Investment in Impaired Loans		1,364	1,413
Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance		107	131
Allowance on Impaired Loans		23	20
Impaired Loans Without a Related Allowance		87	74
Unpaid Contractual Balance		211	240
Total Recorded Investment in Impaired Loans		194	205
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance		84	124
Allowance on Impaired Loans		21	19
Impaired Loans Without a Related Allowance		70	36
Unpaid Contractual Balance		174	178
Total Recorded Investment in Impaired Loans		154	160
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance		23	7
Allowance on Impaired Loans		2	1
Impaired Loans Without a Related Allowance		17	38
Unpaid Contractual Balance		37	62
Total Recorded Investment in Impaired Loans		40	45
Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance		502	658
Allowance on Impaired Loans		104	109
Impaired Loans Without a Related Allowance		668	550
Unpaid Contractual Balance		1,456	1,487
Total Recorded Investment in Impaired Loans		1,170	1,208
Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance		119	157
Allowance on Impaired Loans		16	18
Impaired Loans Without a Related Allowance		311	288
Unpaid Contractual Balance		593	605
Total Recorded Investment in Impaired Loans		430	445
Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance		94	129
Allowance on Impaired Loans		12	11
Impaired Loans Without a Related Allowance		190	141
Unpaid Contractual Balance		351	335
Total Recorded Investment in Impaired Loans		284	270
Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance		22	75
Allowance on Impaired Loans		2	3
Impaired Loans Without a Related Allowance		120	86
Unpaid Contractual Balance		174	193
Total Recorded Investment in Impaired Loans		142	161
Home equity loans serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	[1]	53	75
Allowance on Impaired Loans	[1]	8	9
Impaired Loans Without a Related Allowance	[1]	26	16
Unpaid Contractual Balance	[1]	91	102
Total Recorded Investment in Impaired Loans	[1]	79	91
Home equity lines of credit serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	[1]	3	4
Allowance on Impaired Loans	[1]	1	1
Impaired Loans Without a Related Allowance	[1]	7	7
Unpaid Contractual Balance	[1]	14	14
Total Recorded Investment in Impaired Loans	[1]	10	11
Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance		3	2
Allowance on Impaired Loans		0	1
Impaired Loans Without a Related Allowance		11	9
Unpaid Contractual Balance		18	16
Total Recorded Investment in Impaired Loans		14	11
Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance		164	167
Allowance on Impaired Loans		48	48
Impaired Loans Without a Related Allowance		1	0
Unpaid Contractual Balance		166	167
Total Recorded Investment in Impaired Loans		165	167
Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance		29	32
Allowance on Impaired Loans		12	13
Impaired Loans Without a Related Allowance		0	0
Unpaid Contractual Balance		29	32
Total Recorded Investment in Impaired Loans		29	32
Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance		15	17
Allowance on Impaired Loans		5	5
Impaired Loans Without a Related Allowance		2	3
Unpaid Contractual Balance		20	23
Total Recorded Investment in Impaired Loans		$ 17	$ 20

[1] The Company’s SBO portfolio consists of purchased home equity loans and lines that were originally serviced by others. The Company now services a portion of this portfolio internally.