ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Recorded Investment in Retail Loans by Delinquency Status (Details) - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014
Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total		$ 97,431	$ 93,410
Loans and Leases | Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		12,358	11,352
Total		12,792	11,832
Loans and Leases | Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		2,478	2,997
Total		2,842	3,424
Loans and Leases | Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		14,060	14,705
Total		14,707	15,423
Loans and Leases | Home equity loans serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	[1]	956	1,101
Total	[1]	1,054	1,228
Loans and Leases | Home equity lines of credit serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	[1]	344	455
Total	[1]	441	550
Loans and Leases | Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		12,859	11,839
Total		13,876	12,706
Loans and Leases | Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		3,689	2,106
Total		3,846	2,256
Loans and Leases | Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		1,543	1,615
Total		1,628	1,693
Loans and Leases | Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		902	985
Total		976	1,072
Loans and Leases | Total retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		49,189	47,155
Total		52,162	50,184
Financing Receivables, 1 to 29 Days Past Due | Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		107	114
Financing Receivables, 1 to 29 Days Past Due | Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		179	222
Financing Receivables, 1 to 29 Days Past Due | Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		401	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]	58	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]	56	66
Financing Receivables, 1 to 29 Days Past Due | Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		858	758
Financing Receivables, 1 to 29 Days Past Due | Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		90	108
Financing Receivables, 1 to 29 Days Past Due | Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		51	39
Financing Receivables, 1 to 29 Days Past Due | Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		55	65
Financing Receivables, 1 to 29 Days Past Due | Total retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		1,855	1,897
Financing Receivables 30 To 89 Days Past Due | Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		78	97
Financing Receivables 30 To 89 Days Past Due | Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		46	60
Financing Receivables 30 To 89 Days Past Due | Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		77	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]	21	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]	14	10
Financing Receivables 30 To 89 Days Past Due | Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		130	93
Financing Receivables 30 To 89 Days Past Due | Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		28	25
Financing Receivables 30 To 89 Days Past Due | Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		19	22
Financing Receivables 30 To 89 Days Past Due | Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		15	18
Financing Receivables 30 To 89 Days Past Due | Total retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		428	424
Financing Receivables 90 Days or More Past Due | Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		249	269
Financing Receivables 90 Days or More Past Due | Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		139	145
Financing Receivables 90 Days or More Past Due | Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		169	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]	19	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]	27	19
Financing Receivables 90 Days or More Past Due | Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		29	16
Financing Receivables 90 Days or More Past Due | Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		39	17
Financing Receivables 90 Days or More Past Due | Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		15	17
Financing Receivables 90 Days or More Past Due | Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		4	4
Financing Receivables 90 Days or More Past Due | Total retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due		$ 690	$ 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.