ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Accruing and Nonaccruing Past Due Amounts (Details) - Loans and Leases - USD ($) $ in Millions		Jun. 30, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		$ 1,357	$ 1,356
Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		390	204
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		308	84
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		81	110
Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		1	10
Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		967	1,152
Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		195	316
Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		107	148
Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		275	285
Home equity loans serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	[1]	31	40
Home equity lines of credit serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	[1]	52	45
Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		190	194
Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		71	71
Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		32	36
Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		14	17
Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		293	383
Financing Receivables, 30 to 59 Days Past Due | Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		11	48
Financing Receivables, 30 to 59 Days Past Due | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		8	9
Financing Receivables, 30 to 59 Days Past Due | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		2	30
Financing Receivables, 30 to 59 Days Past Due | Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		1	9
Financing Receivables, 30 to 59 Days Past Due | Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		282	335
Financing Receivables, 30 to 59 Days Past Due | Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		40	54
Financing Receivables, 30 to 59 Days Past Due | Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		20	32
Financing Receivables, 30 to 59 Days Past Due | Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		44	60
Financing Receivables, 30 to 59 Days Past Due | Home equity loans serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	[1]	10	14
Financing Receivables, 30 to 59 Days Past Due | Home equity lines of credit serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	[1]	12	10
Financing Receivables, 30 to 59 Days Past Due | Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		122	127
Financing Receivables, 30 to 59 Days Past Due | Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		18	19
Financing Receivables, 30 to 59 Days Past Due | Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		10	11
Financing Receivables, 30 to 59 Days Past Due | Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		6	8
Financing Receivables 60 To 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		133	124
Financing Receivables 60 To 89 Days Past Due | Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		28	8
Financing Receivables 60 To 89 Days Past Due | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		23	4
Financing Receivables 60 To 89 Days Past Due | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		5	3
Financing Receivables 60 To 89 Days Past Due | Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		0	1
Financing Receivables 60 To 89 Days Past Due | Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		105	116
Financing Receivables 60 To 89 Days Past Due | Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		10	16
Financing Receivables 60 To 89 Days Past Due | Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		8	12
Financing Receivables 60 To 89 Days Past Due | Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		24	20
Financing Receivables 60 To 89 Days Past Due | Home equity loans serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	[1]	4	6
Financing Receivables 60 To 89 Days Past Due | Home equity lines of credit serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	[1]	5	6
Financing Receivables 60 To 89 Days Past Due | Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		31	32
Financing Receivables 60 To 89 Days Past Due | Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		11	11
Financing Receivables 60 To 89 Days Past Due | Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		8	9
Financing Receivables 60 To 89 Days Past Due | Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		4	4
Financing Receivables 90 Days or More Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		931	849
Financing Receivables 90 Days or More Past Due | Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		351	148
Financing Receivables 90 Days or More Past Due | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		277	71
Financing Receivables 90 Days or More Past Due | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		74	77
Financing Receivables 90 Days or More Past Due | Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		0	0
Financing Receivables 90 Days or More Past Due | Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		580	701
Financing Receivables 90 Days or More Past Due | Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		145	246
Financing Receivables 90 Days or More Past Due | Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		79	104
Financing Receivables 90 Days or More Past Due | Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		207	205
Financing Receivables 90 Days or More Past Due | Home equity loans serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	[1]	17	20
Financing Receivables 90 Days or More Past Due | Home equity lines of credit serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	[1]	35	29
Financing Receivables 90 Days or More Past Due | Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		37	35
Financing Receivables 90 Days or More Past Due | Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		42	41
Financing Receivables 90 Days or More Past Due | Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		14	16
Financing Receivables 90 Days or More Past Due | Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		$ 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.