ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Narrative (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Financing Receivable, Modifications [Line Items]
Mortgage loans collateralized by OREO	$ 260,000,000
Larger balance commercial loans minimum balance (greater than)	3,000,000	$ 3,000,000
Commitments to lend additional funds to debtors owing receivables which were TDRs	$ 18,000,000	$ 53,000,000
High loan to value criteria (exceeds)	90.00%	90.00%
Total commercial
Financing Receivable, Modifications [Line Items]
TDR balance	$ 124,000,000	$ 176,000,000
Total retail
Financing Receivable, Modifications [Line Items]
TDR balance	$ 1,200,000,000	$ 1,200,000,000