DERIVATIVES - Cash Flow Hedges (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pretax change in accumulated other comprehensive income (loss)
Total gain (loss) recognized in AOCI	$ (421)	$ (3,606)	$ (898)
Other revenue	67	(21)	1,165
Net interest income	54,900	48,668	42,494
Cash flow hedges expected to be reclassified within 12 months	$ (800)
Maximum length of time hedged in cash flow hedge	15 years
Interest rate contracts
Pretax change in accumulated other comprehensive income (loss)
Total gain (loss) recognized in AOCI	$ (434)	(3,640)	(847)
Foreign exchange contracts
Pretax change in accumulated other comprehensive income (loss)
Total gain (loss) recognized in AOCI	13	34	(51)
Cash flow hedges
Pretax change in accumulated other comprehensive income (loss)
Net interest income	1,480	(3,477)	(1,969)
Amount of gain (loss) reclassified from AOCI to earnings | Cash flow hedges
Pretax change in accumulated other comprehensive income (loss)
Other revenue	(4)	(4)	(4)
Net interest income	(1,897)	(125)	1,075
Amount of gain (loss) reclassified from AOCI to earnings | Cash flow hedges | Interest rate contracts
Pretax change in accumulated other comprehensive income (loss)
Other revenue	0	0	0
Net interest income	(1,897)	(125)	1,075
Amount of gain (loss) reclassified from AOCI to earnings | Cash flow hedges | Foreign exchange contracts
Pretax change in accumulated other comprehensive income (loss)
Other revenue	(4)	(4)	(4)
Net interest income	$ 0	$ 0	$ 0