ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Additional Impaired Loan Information (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	$ 53		$ 32		$ 15
Average Recorded Investment	1,434		1,371		1,231
Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	11		2		2
Average Recorded Investment	296		306		586
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	9		1		1
Average Recorded Investment	198		157		276
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	2		1		1
Average Recorded Investment	98		149		310
Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	42		30		13
Average Recorded Investment	1,138		1,065		645
Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	14		7		4
Average Recorded Investment	429		419		236
Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	8		5		2
Average Recorded Investment	246		228		200
Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	4		2		0
Average Recorded Investment	149		90		38
Home equity loans serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	5	[1]	5	[1]	6	[1]
Average Recorded Investment	91	[1]	102	[1]	118	[1]
Home equity lines of credit serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	0	[1]	0	[1]	0	[1]
Average Recorded Investment	11	[1]	12	[1]	9	[1]
Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	0		0		0
Average Recorded Investment	7		8		5
Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	8		7		0
Average Recorded Investment	153		140		11
Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	2		3		0
Average Recorded Investment	31		41		0
Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	1		1		1
Average Recorded Investment	$ 21		$ 25		$ 28

[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.