ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Accruing and Nonaccruing Past Due Amounts (Details) - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		$ 453	$ 510
90 Days or More Past Due		820	872
Total Past Due		1,273	1,382
Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		25	86
90 Days or More Past Due		130	164
Total Past Due		155	250
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		22	57
90 Days or More Past Due		88	114
Total Past Due		110	171
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		3	26
90 Days or More Past Due		42	50
Total Past Due		45	76
Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		0	3
90 Days or More Past Due		0	0
Total Past Due		0	3
Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		428	424
90 Days or More Past Due		690	708
Total Past Due		1,118	1,132
Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		78	97
90 Days or More Past Due		249	269
Total Past Due		327	366
Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		46	60
90 Days or More Past Due		139	145
Total Past Due		185	205
Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		77	73
90 Days or More Past Due		169	198
Total Past Due		246	271
Home equity loans serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	[1]	21	26
90 Days or More Past Due	[1]	19	23
Total Past Due	[1]	40	49
Home equity lines of credit serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	[1]	14	10
90 Days or More Past Due	[1]	27	19
Total Past Due	[1]	41	29
Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		130	93
90 Days or More Past Due		29	16
Total Past Due		159	109
Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		28	25
90 Days or More Past Due		39	17
Total Past Due		67	42
Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		19	22
90 Days or More Past Due		15	17
Total Past Due		34	39
Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		15	18
90 Days or More Past Due		4	4
Total Past Due		$ 19	$ 22

[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.