GOODWILL - Narrative (Details)	9 Months Ended		213 Months Ended
	Sep. 30, 2015 USD ($) reporting_unit	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) business
Goodwill [Line Items]
Number of acquisitions of banks or assets of banks | business			25
Number of reporting units | reporting_unit	2
Goodwill impairment loss	$ 0	$ 0
Consumer Banking
Goodwill [Line Items]
Goodwill accumulated impairment loss	5,900,000,000	5,900,000,000	$ 5,900,000,000
Commercial Banking
Goodwill [Line Items]
Goodwill accumulated impairment loss	$ 50,000,000	$ 50,000,000	$ 50,000,000