GOODWILL AND INTANGIBLE ASSETS - Changes in Goodwill by Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill
Balance of goodwill at beginning of period	$ 22,126	$ 22,046	$ 22,256
Foreign exchange translation	36	80	(194)
Divestitures			(16)
Balance of goodwill at end of period	22,162	22,126	22,046
Global Consumer Banking
Goodwill
Balance of goodwill at beginning of period	12,102	12,087	12,128
Foreign exchange translation	40	15	(41)
Divestitures			0
Balance of goodwill at end of period	12,142	12,102	12,087
Institutional Clients Group
Goodwill
Balance of goodwill at beginning of period	10,024	9,959	10,112
Foreign exchange translation	(4)	65	(153)
Divestitures			0
Balance of goodwill at end of period	10,020	10,024	9,959
Corporate/Other
Goodwill
Balance of goodwill at beginning of period	0	0	16
Foreign exchange translation	0	0	0
Divestitures			(16)
Balance of goodwill at end of period	$ 0	$ 0	$ 0