GOODWILL AND INTANGIBLE ASSETS - Goodwill Rollforward (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($)
Goodwill [Roll Forward]
Balance at beginning of period	$ 7,044
Business acquisitions	6
Balance at end of period	7,050
Consumer Banking
Goodwill [Roll Forward]
Balance at beginning of period	2,258
Business acquisitions	0
Balance at end of period	2,258
Commercial Banking
Goodwill [Roll Forward]
Balance at beginning of period	4,786
Business acquisitions	6
Balance at end of period	$ 4,792