ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Impaired Loans by Class (Details) - USD ($) $ in Millions		Jun. 30, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance		$ 613	$ 789
Allowance on Impaired Loans		128	129
Impaired Loans Without a Related Allowance		732	624
Unpaid Contractual Balance		1,654	1,727
Total Recorded Investment in Impaired Loans		1,345	1,413
Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance		93	131
Allowance on Impaired Loans		21	20
Impaired Loans Without a Related Allowance		63	74
Unpaid Contractual Balance		182	240
Total Recorded Investment in Impaired Loans		156	205
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance		80	124
Allowance on Impaired Loans		21	19
Impaired Loans Without a Related Allowance		44	36
Unpaid Contractual Balance		152	178
Total Recorded Investment in Impaired Loans		124	160
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance		13	7
Allowance on Impaired Loans		0	1
Impaired Loans Without a Related Allowance		19	38
Unpaid Contractual Balance		30	62
Total Recorded Investment in Impaired Loans		32	45
Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance		520	658
Allowance on Impaired Loans		107	109
Impaired Loans Without a Related Allowance		669	550
Unpaid Contractual Balance		1,472	1,487
Total Recorded Investment in Impaired Loans		1,189	1,208
Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance		124	157
Allowance on Impaired Loans		17	18
Impaired Loans Without a Related Allowance		314	288
Unpaid Contractual Balance		599	605
Total Recorded Investment in Impaired Loans		438	445
Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance		98	129
Allowance on Impaired Loans		13	11
Impaired Loans Without a Related Allowance		179	141
Unpaid Contractual Balance		342	335
Total Recorded Investment in Impaired Loans		277	270
Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance		24	75
Allowance on Impaired Loans		2	3
Impaired Loans Without a Related Allowance		128	86
Unpaid Contractual Balance		184	193
Total Recorded Investment in Impaired Loans		152	161
Home equity loans serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	[1]	57	75
Allowance on Impaired Loans	[1]	9	9
Impaired Loans Without a Related Allowance	[1]	27	16
Unpaid Contractual Balance	[1]	96	102
Total Recorded Investment in Impaired Loans	[1]	84	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]	8	7
Unpaid Contractual Balance	[1]	15	14
Total Recorded Investment in Impaired Loans	[1]	11	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		10	9
Unpaid Contractual Balance		18	16
Total Recorded Investment in Impaired Loans		13	11
Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance		166	167
Allowance on Impaired Loans		48	48
Impaired Loans Without a Related Allowance		1	0
Unpaid Contractual Balance		168	167
Total Recorded Investment in Impaired Loans		167	167
Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance		30	32
Allowance on Impaired Loans		12	13
Impaired Loans Without a Related Allowance		0	0
Unpaid Contractual Balance		30	32
Total Recorded Investment in Impaired Loans		30	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.