GOODWILL AND INTANGIBLE ASSETS - Changes in Goodwill (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020
Goodwill
Balance of goodwill at beginning of period	$ 21,399	$ 21,264	$ 22,126
Foreign currency translation	225	135	(862)
Balance of goodwill at end of period	21,624	21,399	21,264
Global Consumer Banking
Goodwill
Balance of goodwill at beginning of period	11,876	11,837	12,102
Foreign currency translation	74	39	(265)
Balance of goodwill at end of period	11,950	11,876	11,837
Institutional Clients Group
Goodwill
Balance of goodwill at beginning of period	9,523	9,427	10,024
Foreign currency translation	151	96	(597)
Balance of goodwill at end of period	$ 9,674	$ 9,523	$ 9,427