ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Impaired Loans by Class (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	$ 650		$ 789
Allowance on Impaired Loans	142		129
Impaired Loans Without a Related Allowance	746		624
Unpaid Contractual Balance	1,711		1,727
Total Recorded Investment in Impaired Loans	1,396		1,413
Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	117		131
Allowance on Impaired Loans	35		20
Impaired Loans Without a Related Allowance	77		74
Unpaid Contractual Balance	227		240
Total Recorded Investment in Impaired Loans	194		205
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	97		124
Allowance on Impaired Loans	30		19
Impaired Loans Without a Related Allowance	41		36
Unpaid Contractual Balance	163		178
Total Recorded Investment in Impaired Loans	138		160
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	20		7
Allowance on Impaired Loans	5		1
Impaired Loans Without a Related Allowance	36		38
Unpaid Contractual Balance	64		62
Total Recorded Investment in Impaired Loans	56		45
Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	533		658
Allowance on Impaired Loans	107		109
Impaired Loans Without a Related Allowance	669		550
Unpaid Contractual Balance	1,484		1,487
Total Recorded Investment in Impaired Loans	1,202		1,208
Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	129		157
Allowance on Impaired Loans	17		18
Impaired Loans Without a Related Allowance	316		288
Unpaid Contractual Balance	605		605
Total Recorded Investment in Impaired Loans	445		445
Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	100		129
Allowance on Impaired Loans	11		11
Impaired Loans Without a Related Allowance	173		141
Unpaid Contractual Balance	337		335
Total Recorded Investment in Impaired Loans	273		270
Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	27		75
Allowance on Impaired Loans	2		3
Impaired Loans Without a Related Allowance	130		86
Unpaid Contractual Balance	191		193
Total Recorded Investment in Impaired Loans	157		161
Home equity loans serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	59	[1]	75	[1]
Allowance on Impaired Loans	9	[1]	9	[1]
Impaired Loans Without a Related Allowance	29	[1]	16	[1]
Unpaid Contractual Balance	100	[1]	102	[1]
Total Recorded Investment in Impaired Loans	88	[1]	91	[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]	4	[1]
Allowance on Impaired Loans	1	[1]	1	[1]
Impaired Loans Without a Related Allowance	7	[1]	7	[1]
Unpaid Contractual Balance	14	[1]	14	[1]
Total Recorded Investment in Impaired Loans	11	[1]	11	[1]
Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	2		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	12		11
Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	165		167
Allowance on Impaired Loans	49		48
Impaired Loans Without a Related Allowance	1		0
Unpaid Contractual Balance	166		167
Total Recorded Investment in Impaired Loans	166		167
Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	31		32
Allowance on Impaired Loans	13		13
Impaired Loans Without a Related Allowance	0		0
Unpaid Contractual Balance	31		32
Total Recorded Investment in Impaired Loans	31		32
Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Impaired Loans With a Related Allowance	16		17
Allowance on Impaired Loans	5		5
Impaired Loans Without a Related Allowance	3		3
Unpaid Contractual Balance	22		23
Total Recorded Investment in Impaired Loans	$ 19		$ 20

[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.