DERIVATIVES - Cash Flow Hedges (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pretax change in accumulated other comprehensive income (loss)
Total gain (loss) recognized in AOCI	$ (898)	$ 2,655	$ 729
Other revenue	1,165	420	1,448
Net interest revenue	42,494	44,751	48,128
Cash flow hedges expected to be reclassified within 12 months	$ 614
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	$ (847)	2,670	746
Foreign exchange contracts
Pretax change in accumulated other comprehensive income (loss)
Total gain (loss) recognized in AOCI	(51)	(15)	(17)
Cash flow hedges
Pretax change in accumulated other comprehensive income (loss)
Net interest revenue	(1,969)	1,925	1,120
Amount of gain (loss) reclassified from AOCI to earnings \| Cash flow hedges
Pretax change in accumulated other comprehensive income (loss)
Other revenue	(4)	(4)	(7)
Net interest revenue	1,075	734	(384)
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 revenue	1,075	734	(384)
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)	(7)
Net interest revenue	$ 0	$ 0	$ 0

The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

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The net amount of operating interest income (expense).

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Maximum length of time over which the entity is hedging its exposure to the variability in future cash flows for forecasted transactions, excluding those forecasted transactions related to the payment of variable interest on existing financial instruments, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount, before tax and after reclassification, of gain (loss) from derivative instrument designated and qualifying cash flow hedge included in assessment of hedge effectiveness, attributable to parent.

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Amount of income (expense) related to nonoperating activities, classified as other.

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