GOODWILL AND INTANGIBLE ASSETS - Changes in Goodwill by Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill
Balance of goodwill at beginning of period	$ 22,256	$ 21,659	$ 22,349
Foreign exchange translation and other	(194)	729	(613)
Divestitures	(16)	(104)	(77)
Impairment of goodwill		(28)
Balance of goodwill at end of period	22,046	22,256	21,659
Global Consumer Banking
Goodwill
Balance of goodwill at beginning of period	12,784	12,530
Foreign exchange translation and other	(41)	286
Divestitures	0	(32)
Impairment of goodwill		0
Balance of goodwill at end of period	12,743	12,784	12,530
Institutional Clients Group
Goodwill
Balance of goodwill at beginning of period	9,456	9,085
Foreign exchange translation and other	(153)	443
Divestitures	0	(72)
Impairment of goodwill		0
Balance of goodwill at end of period	9,303	9,456	9,085
Corporate/Other
Goodwill
Balance of goodwill at beginning of period	16	44
Foreign exchange translation and other	0	0
Divestitures	(16)	0
Impairment of goodwill		(28)
Balance of goodwill at end of period	$ 0	$ 16	$ 44