DERIVATIVES - Fair Value Hedges (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Gain (loss) on fair value hedges
Gain (loss) under mark-to-market approach	$ 51	$ 41
Gain (loss) under amortization approach	19	11
Excluded component of fair value hedges | Excluded component of fair value hedges
Gain (loss) on fair value hedges
Other comprehensive income (loss), pretax	2	22	$ (2)	$ (4)
Other revenue
Gain (loss) on fair value hedges
Gain (loss) on the hedging derivatives included in assessment of the effectiveness of fair value hedges	(144)	921	1,305	961
Gain (loss) on the hedged item in designated and qualifying fair value hedges	144	(921)	(1,305)	(961)
Net gain (loss) on the hedging derivatives excluded from assessment of the effectiveness of fair value hedges	102	54	170	125
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	(436)	(491)	(1,040)	(492)
Gain (loss) on the hedged item in designated and qualifying fair value hedges	448	488	1,068	481
Net gain (loss) on the hedging derivatives excluded from assessment of the effectiveness of fair value hedges	0	0	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	0	0
Gain (loss) on the hedged item in designated and qualifying fair value hedges	0	0	0	0
Net gain (loss) on the hedging derivatives excluded from assessment of the effectiveness of fair value hedges	0	0	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	(436)	(491)	(1,040)	(492)
Gain (loss) on the hedged item in designated and qualifying fair value hedges	448	488	1,068	481
Net gain (loss) on the hedging derivatives excluded from assessment of the effectiveness of fair value hedges	0	0	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	145	738	74	1,286
Gain (loss) on the hedged item in designated and qualifying fair value hedges	(145)	(738)	(74)	(1,286)
Net gain (loss) on the hedging derivatives excluded from assessment of the effectiveness of fair value hedges	32	2	3	24
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	0	0
Gain (loss) on the hedged item in designated and qualifying fair value hedges	0	0	0	0
Net gain (loss) on the hedging derivatives excluded from assessment of the effectiveness of fair value hedges	0	0	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	(289)	183	1,231	(325)
Gain (loss) on the hedged item in designated and qualifying fair value hedges	289	(183)	(1,231)	325
Net gain (loss) on the hedging derivatives excluded from assessment of the effectiveness of fair value hedges	70	52	167	101
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	0	0
Gain (loss) on the hedged item in designated and qualifying fair value hedges	0	0	0	0
Net gain (loss) on the hedging derivatives excluded from assessment of the effectiveness of fair value hedges	$ 0	$ 0	$ 0	$ 0