ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Impaired Loans by Class (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	$ 789		$ 832
Allowance on Impaired Loans	129		131
Impaired Loans Without a Related Allowance	624		607
Unpaid Contractual Balance	1,727		1,885
Total Recorded Investment in Impaired Loans	1,413		1,439
Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	131		162
Allowance on Impaired Loans	20		23
Impaired Loans Without a Related Allowance	74		77
Unpaid Contractual Balance	240		435
Total Recorded Investment in Impaired Loans	205		239
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	124		86
Allowance on Impaired Loans	19		15
Impaired Loans Without a Related Allowance	36		33
Unpaid Contractual Balance	178		214
Total Recorded Investment in Impaired Loans	160		119
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	7		76
Allowance on Impaired Loans	1		8
Impaired Loans Without a Related Allowance	38		44
Unpaid Contractual Balance	62		221
Total Recorded Investment in Impaired Loans	45		120
Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	658		670
Allowance on Impaired Loans	109		108
Impaired Loans Without a Related Allowance	550		530
Unpaid Contractual Balance	1,487		1,450
Total Recorded Investment in Impaired Loans	1,208		1,200
Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	157		174
Allowance on Impaired Loans	18		42
Impaired Loans Without a Related Allowance	288		267
Unpaid Contractual Balance	605		588
Total Recorded Investment in Impaired Loans	445		441
Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	129		104
Allowance on Impaired Loans	11		17
Impaired Loans Without a Related Allowance	141		143
Unpaid Contractual Balance	335		301
Total Recorded Investment in Impaired Loans	270		247
Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	75		77
Allowance on Impaired Loans	3		0
Impaired Loans Without a Related Allowance	86		87
Unpaid Contractual Balance	193		192
Total Recorded Investment in Impaired Loans	161		164
Home equity loans serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	75	[1]	86	[1]
Allowance on Impaired Loans	9	[1]	10	[1]
Impaired Loans Without a Related Allowance	16	[1]	14	[1]
Unpaid Contractual Balance	102	[1]	110	[1]
Total Recorded Investment in Impaired Loans	91	[1]	100	[1]
Home equity lines of credit serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	4	[1]	5	[1]
Allowance on Impaired Loans	1	[1]	1	[1]
Impaired Loans Without a Related Allowance	7	[1]	7	[1]
Unpaid Contractual Balance	14	[1]	15	[1]
Total Recorded Investment in Impaired Loans	11	[1]	12	[1]
Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	2		2
Allowance on Impaired Loans	1		0
Impaired Loans Without a Related Allowance	9		8
Unpaid Contractual Balance	16		15
Total Recorded Investment in Impaired Loans	11		10
Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	167		159
Allowance on Impaired Loans	48		21
Impaired Loans Without a Related Allowance	0		0
Unpaid Contractual Balance	167		159
Total Recorded Investment in Impaired Loans	167		159
Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	32		42
Allowance on Impaired Loans	13		14
Impaired Loans Without a Related Allowance	0		0
Unpaid Contractual Balance	32		42
Total Recorded Investment in Impaired Loans	32		42
Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	17		21
Allowance on Impaired Loans	5		3
Impaired Loans Without a Related Allowance	3		4
Unpaid Contractual Balance	23		28
Total Recorded Investment in Impaired Loans	$ 20		$ 25

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