ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Additional Impaired Loan Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	$ 12		$ 11
Average Recorded Investment	1,381		1,409
Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	1		1
Average Recorded Investment	193		219
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	1		0
Average Recorded Investment	142		102
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	0		1
Average Recorded Investment	51		117
Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	11		10
Average Recorded Investment	1,188		1,190
Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	4		3
Average Recorded Investment	441		442
Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	2		2
Average Recorded Investment	268		248
Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	1		1
Average Recorded Investment	156		159
Home equity loans serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	1	[1]	1	[1]
Average Recorded Investment	88	[1]	101	[1]
Home equity lines of credit serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	0	[1]	0	[1]
Average Recorded Investment	11	[1]	11	[1]
Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	0		0
Average Recorded Investment	11		9
Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	2		2
Average Recorded Investment	164		158
Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	1		1
Average Recorded Investment	30		39
Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	0		0
Average Recorded Investment	$ 19		$ 23

[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.