GOODWILL AND INTANGIBLE ASSETS - Changes in Goodwill (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021 USD ($)
Goodwill
Balance of goodwill at beginning of period	$ 22,162
Foreign currency translation	(257)
Balance of goodwill at end of period	21,905
Global Consumer Banking
Goodwill
Balance of goodwill at beginning of period	12,142
Foreign currency translation	(68)
Balance of goodwill at end of period	12,074
Institutional Clients Group
Goodwill
Balance of goodwill at beginning of period	10,020
Foreign currency translation	(189)
Balance of goodwill at end of period	$ 9,831