ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Narrative (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Modifications [Line Items]
Larger balance commercial loans minimum balance	$ 3	$ 3
Commitments to lend additional funds to debtors owing receivables which were TDRs	53	52
High loan to value criteria	90.00%	90.00%
Total commercial
Financing Receivable, Modifications [Line Items]
TDR balance	176	167
Total retail
Financing Receivable, Modifications [Line Items]
TDR balance	1,200	1,200
Allowance for loan and lease losses
Financing Receivable, Modifications [Line Items]
Loss period change		0
Allowance for loan and lease losses | Retail
Financing Receivable, Modifications [Line Items]
Loss period change		$ 96