ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Other Nonperforming Assets (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Other nonperforming assets, net of valuation allowance	$ 48	$ 46
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Other nonperforming assets, net of valuation allowance	1	1
Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Other nonperforming assets, net of valuation allowance	$ 47	$ 45