ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Summary of Allowance for Credit Losses by Evaluation Method (Details) (Loans and Leases, USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually evaluated	$ 130	$ 131
Formula-based evaluation	1,134	1,129
Allowance for credit losses	1,264	1,260
Total commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually evaluated	14	23
Formula-based evaluation	591	514
Allowance for credit losses	605	537
Total retail
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually evaluated	116	108
Formula-based evaluation	543	615
Allowance for credit losses	$ 659	$ 723