ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Other Nonperforming Assets (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming assets, net of valuation allowance	$ 46	$ 42
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming assets, net of valuation allowance	1	3
Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming assets, net of valuation allowance	$ 45	$ 39