ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Accruing and Nonaccruing Past Due Amounts (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		$ 507	$ 510
90 Days or More Past Due		849	872
Total Past Due		1,356	1,382
Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		56	86
90 Days or More Past Due		148	164
Total Past Due		204	250
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		13	57
90 Days or More Past Due		71	114
Total Past Due		84	171
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		33	26
90 Days or More Past Due		77	50
Total Past Due		110	76
Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		10	3
90 Days or More Past Due		0	0
Total Past Due		10	3
Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		451	424
90 Days or More Past Due		701	708
Total Past Due		1,152	1,132
Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		70	97
90 Days or More Past Due		246	269
Total Past Due		316	366
Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		44	60
90 Days or More Past Due		104	145
Total Past Due		148	205
Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		80	73
90 Days or More Past Due		205	198
Total Past Due		285	271
Home equity loans serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	[1]	20	26
90 Days or More Past Due	[1]	20	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]	16	10
90 Days or More Past Due	[1]	29	19
Total Past Due	[1]	45	29
Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		159	93
90 Days or More Past Due		35	16
Total Past Due		194	109
Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		30	25
90 Days or More Past Due		41	17
Total Past Due		71	42
Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		20	22
90 Days or More Past Due		16	17
Total Past Due		36	39
Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		12	18
90 Days or More Past Due		5	4
Total Past Due		$ 17	$ 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.