DERIVATIVES - Fair Value Hedges (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Gain (loss) on fair value hedges
Gain (loss) under mark-to-market approach	$ 93	$ 45
Gain (loss) under amortization approach	5	4
Excluded component of fair value hedges | Excluded component of fair value hedges
Gain (loss) on fair value hedges
Other comprehensive income (loss), pretax	(4)	(26)
Other revenue
Gain (loss) on fair value hedges
Gain (loss) on the hedging derivatives included in assessment of the effectiveness of fair value hedges	1,449	40
Gain (loss) on the hedged item in designated and qualifying fair value hedges	(1,449)	(40)
Net gain (loss) on the hedging derivatives excluded from assessment of the effectiveness of fair value hedges	69	71
Net interest income
Gain (loss) on fair value hedges
Gain (loss) on the hedging derivatives included in assessment of the effectiveness of fair value hedges	(604)	(1)
Gain (loss) on the hedged item in designated and qualifying fair value hedges	620	(7)
Net gain (loss) on the hedging derivatives excluded from assessment of the effectiveness of fair value hedges	0	0
Interest rate contracts (gross) | Other revenue
Gain (loss) on fair value hedges
Gain (loss) on the hedging derivatives included in assessment of the effectiveness of fair value hedges	0	0
Gain (loss) on the hedged item in designated and qualifying fair value hedges	0	0
Net gain (loss) on the hedging derivatives excluded from assessment of the effectiveness of fair value hedges	0	0
Interest rate contracts (gross) | Net interest income
Gain (loss) on fair value hedges
Gain (loss) on the hedging derivatives included in assessment of the effectiveness of fair value hedges	(604)	(1)
Gain (loss) on the hedged item in designated and qualifying fair value hedges	620	(7)
Net gain (loss) on the hedging derivatives excluded from assessment of the effectiveness of fair value hedges	0	0
Foreign exchange contracts (gross) | Other revenue
Gain (loss) on fair value hedges
Gain (loss) on the hedging derivatives included in assessment of the effectiveness of fair value hedges	(71)	548
Gain (loss) on the hedged item in designated and qualifying fair value hedges	71	(548)
Net gain (loss) on the hedging derivatives excluded from assessment of the effectiveness of fair value hedges	(29)	22
Foreign exchange contracts (gross) | Net interest income
Gain (loss) on fair value hedges
Gain (loss) on the hedging derivatives included in assessment of the effectiveness of fair value hedges	0	0
Gain (loss) on the hedged item in designated and qualifying fair value hedges	0	0
Net gain (loss) on the hedging derivatives excluded from assessment of the effectiveness of fair value hedges	0	0
Commodity hedges | Other revenue
Gain (loss) on fair value hedges
Gain (loss) on the hedging derivatives included in assessment of the effectiveness of fair value hedges	1,520	(508)
Gain (loss) on the hedged item in designated and qualifying fair value hedges	(1,520)	508
Net gain (loss) on the hedging derivatives excluded from assessment of the effectiveness of fair value hedges	98	49
Commodity hedges | Net interest income
Gain (loss) on fair value hedges
Gain (loss) on the hedging derivatives included in assessment of the effectiveness of fair value hedges	0	0
Gain (loss) on the hedged item in designated and qualifying fair value hedges	0	0
Net gain (loss) on the hedging derivatives excluded from assessment of the effectiveness of fair value hedges	$ 0	$ 0