ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Additional Impaired Loan Information (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized		$ 12	$ 12	$ 24	$ 22
Average Recorded Investment		1,357	1,386	1,350	1,372
Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized		1	1	2	1
Average Recorded Investment		180	190	187	198
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized		1	1	1	1
Average Recorded Investment		129	96	133	102
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized		0	0	1	0
Average Recorded Investment		51	94	54	96
Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized		11	11	22	21
Average Recorded Investment		1,177	1,196	1,163	1,174
Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized		4	4	8	7
Average Recorded Investment		436	444	433	437
Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized		3	2	5	4
Average Recorded Investment		272	257	266	249
Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized		1	1	2	2
Average Recorded Investment		151	160	150	157
Home equity loans serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	[1]	1	2	2	3
Average Recorded Investment	[1]	84	101	84	100
Home equity lines of credit serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	[1]	0	0	0	0
Average Recorded Investment	[1]	10	8	10	8
Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized		0	0	0	0
Average Recorded Investment		12	8	11	8
Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized		2	2	4	4
Average Recorded Investment		164	159	162	156
Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized		0	0	1	1
Average Recorded Investment		30	37	29	36
Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized		0	0	0	0
Average Recorded Investment		$ 18	$ 22	$ 18	$ 23

[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.