PREMISES, EQUIPMENT, AND SOFTWARE - Schedule of Premises and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Total premises and equipment, gross	$ 2,445	$ 2,326
Less: accumulated depreciation	(1,844)	(1,731)
Total premises and equipment, net	$ 601	595
Land and land improvements
Property, Plant and Equipment [Line Items]
Useful life	15 years
Total premises and equipment, gross	$ 47	25
Buildings and leasehold improvements
Property, Plant and Equipment [Line Items]
Total premises and equipment, gross	$ 684	634
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	$ 1,714	$ 1,667
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