BUSINESS SEGMENTS - Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) segment	Sep. 30, 2014 USD ($)
Segment Reporting Information [Line Items]
Number of segments | segment			2
Revenues	$ 1,209	$ 1,161	$ 3,592	$ 3,800
Consumer Banking
Segment Reporting Information [Line Items]
Revenues	791	758	2,317	2,296
Consumer Banking | Maximum
Segment Reporting Information [Line Items]
Revenues			25
Commercial Banking
Segment Reporting Information [Line Items]
Revenues	$ 399	$ 374	1,169	$ 1,108
Commercial Banking | Minimum
Segment Reporting Information [Line Items]
Revenues			25
Commercial Banking | Maximum
Segment Reporting Information [Line Items]
Revenues			$ 2,500