ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Other Nonperforming Assets (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming assets, net of valuation allowance	$ 37	$ 49
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming assets, net of valuation allowance	0	0
Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming assets, net of valuation allowance	$ 37	$ 49