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, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Financing Receivable, Recorded Investment, Past Due [Line Items]
Investment in loan balance	$ 93,410		$ 85,859
Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Investment in loan balance	50,184		46,464
Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	11,352		9,236
1-29 Days Past Due	114		114
30-89 Days Past Due	97		115
90 Days or More Past Due	269		261
Investment in loan balance	11,832		9,726
Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	2,997		3,808
1-29 Days Past Due	222		257
30-89 Days Past Due	60		68
90 Days or More Past Due	145		168
Investment in loan balance	3,424		4,301
Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	14,705		14,868
1-29 Days Past Due	447		490
30-89 Days Past Due	73		76
90 Days or More Past Due	198		233
Investment in loan balance	15,423		15,667
Home equity loans serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	1,101	[1]	1,340	[1]
1-29 Days Past Due	78	[1]	84	[1]
30-89 Days Past Due	26	[1]	32	[1]
90 Days or More Past Due	23	[1]	36	[1]
Investment in loan balance	1,228	[1]	1,492	[1]
Home equity lines of credit serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	455	[1]	561	[1]
1-29 Days Past Due	66	[1]	83	[1]
30-89 Days Past Due	10	[1]	11	[1]
90 Days or More Past Due	19	[1]	24	[1]
Investment in loan balance	550	[1]	679	[1]
Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	11,839		8,863
1-29 Days Past Due	758		481
30-89 Days Past Due	93		44
90 Days or More Past Due	16		9
Investment in loan balance	12,706		9,397
Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	2,106		2,012
1-29 Days Past Due	108		118
30-89 Days Past Due	25		45
90 Days or More Past Due	17		33
Investment in loan balance	2,256		2,208
Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	1,615		1,581
1-29 Days Past Due	39		67
30-89 Days Past Due	22		22
90 Days or More Past Due	17		21
Investment in loan balance	1,693		1,691
Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	985		1,205
1-29 Days Past Due	65		69
30-89 Days Past Due	18		22
90 Days or More Past Due	4		7
Investment in loan balance	1,072		1,303
Total retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	47,155		43,474
1-29 Days Past Due	1,897		1,763
30-89 Days Past Due	424		435
90 Days or More Past Due	708		792
Investment in loan balance	$ 50,184		$ 46,464

[1] The Company's SBO portfolio consists of home equity loans and lines that were originally serviced by others. The Company now services a portion of this portfolio internally.