ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Recorded Investment in Retail Loans by Delinquency Status (Details) - Loans and Leases - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total		$ 99,042	$ 93,410
Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		12,905	11,352
Total		13,318	11,832
Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		2,245	2,997
Total		2,557	3,424
Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		13,982	14,705
Total		14,674	15,423
Home equity loans serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	[1]	886	1,101
Total	[1]	986	1,228
Home equity lines of credit serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	[1]	296	455
Total	[1]	389	550
Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		12,670	11,839
Total		13,828	12,706
Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		4,175	2,106
Total		4,359	2,256
Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		1,554	1,615
Total		1,634	1,693
Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		1,013	985
Total		1,083	1,072
Total retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		49,726	47,155
Total		52,828	50,184
Financing Receivables, 1 to 29 Days Past Due | Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		97	114
Financing Receivables, 1 to 29 Days Past Due | Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		164	222
Financing Receivables, 1 to 29 Days Past Due | Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		407	447
Financing Receivables, 1 to 29 Days Past Due | Home equity loans serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	[1]	60	78
Financing Receivables, 1 to 29 Days Past Due | Home equity lines of credit serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	[1]	48	66
Financing Receivables, 1 to 29 Days Past Due | Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		964	758
Financing Receivables, 1 to 29 Days Past Due | Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		113	108
Financing Receivables, 1 to 29 Days Past Due | Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		44	39
Financing Receivables, 1 to 29 Days Past Due | Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		53	65
Financing Receivables, 1 to 29 Days Past Due | Total retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		1,950	1,897
Financing Receivables 30 To 89 Days Past Due | Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		70	97
Financing Receivables 30 To 89 Days Past Due | Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		44	60
Financing Receivables 30 To 89 Days Past Due | Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		80	73
Financing Receivables 30 To 89 Days Past Due | Home equity loans serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	[1]	20	26
Financing Receivables 30 To 89 Days Past Due | Home equity lines of credit serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	[1]	16	10
Financing Receivables 30 To 89 Days Past Due | Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		159	93
Financing Receivables 30 To 89 Days Past Due | Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		30	25
Financing Receivables 30 To 89 Days Past Due | Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		20	22
Financing Receivables 30 To 89 Days Past Due | Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		12	18
Financing Receivables 30 To 89 Days Past Due | Total retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		451	424
Financing Receivables 90 Days or More Past Due | Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		246	269
Financing Receivables 90 Days or More Past Due | Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		104	145
Financing Receivables 90 Days or More Past Due | Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		205	198
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]	20	23
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]	29	19
Financing Receivables 90 Days or More Past Due | Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		35	16
Financing Receivables 90 Days or More Past Due | Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		41	17
Financing Receivables 90 Days or More Past Due | Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		16	17
Financing Receivables 90 Days or More Past Due | Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		5	4
Financing Receivables 90 Days or More Past Due | Total retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		$ 701	$ 708

[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.