DERIVATIVES ACTIVITIES - Cash Flow Hedges (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Pretax change in accumulated other comprehensive income (loss)
Total gain (loss) recognized in AOCI	$ (316)	$ 41
Other revenue	334	248
Net interest revenue	11,172	10,955
Revenue	18,872	18,366
Cash flow hedge gain expected to be reclassified from AOCI within 12 months	$ 142
Maximum length of time hedged in cash flow hedge	10 years
Interest rate contracts
Pretax change in accumulated other comprehensive income (loss)
Total gain (loss) recognized in AOCI	$ (322)	41
Foreign exchange contracts
Pretax change in accumulated other comprehensive income (loss)
Total gain (loss) recognized in AOCI	6	0
Cash flow hedges | (Gain) loss reclassified from AOCI
Pretax change in accumulated other comprehensive income (loss)
Other revenue	2
Net interest revenue	(31)
Revenue		41
Cash flow hedges | (Gain) loss reclassified from AOCI | Interest rate contracts
Pretax change in accumulated other comprehensive income (loss)
Other revenue	0
Net interest revenue	(31)
Revenue		44
Cash flow hedges | (Gain) loss reclassified from AOCI | Foreign exchange contracts
Pretax change in accumulated other comprehensive income (loss)
Other revenue	2
Net interest revenue	$ 0
Revenue		$ (3)