GOODWILL AND INTANGIBLE ASSETS - Changes in Goodwill (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Goodwill
Balance of goodwill at beginning of period	$ 22,256
Foreign exchange translation and other	419
Divestiture	(16)
Balance of goodwill at end of period	22,659
Global Consumer Banking
Goodwill
Balance of goodwill at beginning of period	12,784
Foreign exchange translation and other	184
Divestiture	0
Balance of goodwill at end of period	12,968
Institutional Clients Group
Goodwill
Balance of goodwill at beginning of period	9,456
Foreign exchange translation and other	235
Divestiture	0
Balance of goodwill at end of period	9,691
Corporate/Other
Goodwill
Balance of goodwill at beginning of period	16
Foreign exchange translation and other	0
Divestiture	(16)
Balance of goodwill at end of period	$ 0