DERIVATIVES - Cash Flow Hedges (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Pretax change in accumulated other comprehensive income (loss)
Amount of gain (loss) recognized in AOCI on derivative	$ 307	$ 9
Net pretax change in cash flow hedges included within AOCI		479
Cash flow hedge gain expected to be reclassified from AOCI within 12 months	$ (600)
Maximum length of time hedged in cash flow hedge	14 years
Cash flow hedges | Excluded component of fair value hedges
Pretax change in accumulated other comprehensive income (loss)
Other comprehensive income (loss), pretax	$ 650	479
Interest rate contracts
Pretax change in accumulated other comprehensive income (loss)
Amount of gain (loss) recognized in AOCI on derivative	306	21
Foreign exchange contracts
Pretax change in accumulated other comprehensive income (loss)
Amount of gain (loss) recognized in AOCI on derivative	1	(12)
Other revenue
Pretax change in accumulated other comprehensive income (loss)
Amount of gain (loss) reclassified from AOCI to earnings	(1)	(1)
Other revenue | Interest rate contracts
Pretax change in accumulated other comprehensive income (loss)
Amount of gain (loss) reclassified from AOCI to earnings	0	0
Other revenue | Foreign exchange contracts
Pretax change in accumulated other comprehensive income (loss)
Amount of gain (loss) reclassified from AOCI to earnings	(1)	(1)
Net interest income
Pretax change in accumulated other comprehensive income (loss)
Amount of gain (loss) reclassified from AOCI to earnings	(342)	(469)
Net interest income | Interest rate contracts
Pretax change in accumulated other comprehensive income (loss)
Amount of gain (loss) reclassified from AOCI to earnings	(342)	(469)
Net interest income | Foreign exchange contracts
Pretax change in accumulated other comprehensive income (loss)
Amount of gain (loss) reclassified from AOCI to earnings	$ 0	$ 0