PREMISES, EQUIPMENT, AND SOFTWARE - Schedule of Premises and Equipment (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) sale-leaseback	Dec. 31, 2014 USD ($) sale-leaseback	Dec. 31, 2013 sale-leaseback
Property, Plant and Equipment [Line Items]
Total premises and equipment, gross	$ 2,326	$ 2,246
Less: accumulated depreciation	1,731	1,651
Total premises and equipment, net	$ 595	$ 595
Number of sale-leaseback transactions entered into during period | sale-leaseback	2	0	1
Land and land improvements
Property, Plant and Equipment [Line Items]
Useful life	15 years
Total premises and equipment, gross	$ 25	$ 26
Buildings and leasehold improvements
Property, Plant and Equipment [Line Items]
Total premises and equipment, gross	$ 634	607
Buildings and leasehold improvements | Minimum
Property, Plant and Equipment [Line Items]
Useful life	7 years
Buildings and leasehold improvements | Maximum
Property, Plant and Equipment [Line Items]
Useful life	40 years
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Total premises and equipment, gross	$ 1,667	$ 1,613
Furniture, fixtures and equipment | Minimum
Property, Plant and Equipment [Line Items]
Useful life	5 years
Furniture, fixtures and equipment | Maximum
Property, Plant and Equipment [Line Items]
Useful life	15 years