ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Nonperforming Loans and Leases by Class (Details) - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccruing		$ 1,019	$ 1,093
Accruing and 90 Days or More Delinquent		15	8
Total Nonperforming Loans and Leases		1,034	1,101
Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccruing		123	163
Accruing and 90 Days or More Delinquent		7	1
Total Nonperforming Loans and Leases		130	164
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccruing		81	113
Accruing and 90 Days or More Delinquent		7	1
Total Nonperforming Loans and Leases		88	114
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccruing		42	50
Accruing and 90 Days or More Delinquent		0	0
Total Nonperforming Loans and Leases		42	50
Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccruing		0	0
Accruing and 90 Days or More Delinquent		0	0
Total Nonperforming Loans and Leases		0	0
Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccruing		896	930
Accruing and 90 Days or More Delinquent		8	7
Total Nonperforming Loans and Leases		904	937
Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccruing		324	345
Accruing and 90 Days or More Delinquent		0	0
Total Nonperforming Loans and Leases		324	345
Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccruing		200	203
Accruing and 90 Days or More Delinquent		0	0
Total Nonperforming Loans and Leases		200	203
Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccruing		214	257
Accruing and 90 Days or More Delinquent		0	0
Total Nonperforming Loans and Leases		214	257
Home equity loans serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccruing	[1]	39	47
Accruing and 90 Days or More Delinquent	[1]	0	0
Total Nonperforming Loans and Leases	[1]	39	47
Home equity lines of credit serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccruing	[1]	31	25
Accruing and 90 Days or More Delinquent	[1]	0	0
Total Nonperforming Loans and Leases	[1]	31	25
Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccruing		38	21
Accruing and 90 Days or More Delinquent		0	0
Total Nonperforming Loans and Leases		38	21
Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccruing		32	11
Accruing and 90 Days or More Delinquent		7	6
Total Nonperforming Loans and Leases		39	17
Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccruing		15	16
Accruing and 90 Days or More Delinquent		0	1
Total Nonperforming Loans and Leases		15	17
Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccruing		3	5
Accruing and 90 Days or More Delinquent		1	0
Total Nonperforming Loans and Leases		$ 4	$ 5

[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.