DERIVATIVES ACTIVITIES - Cash Flow Hedges (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Pretax change in accumulated other comprehensive income (loss)
Total gain (loss) recognized in AOCI	$ (149)	$ (43)	$ (669)	$ 96
Other revenue	308	268	1,163	404
Net interest revenue	11,802	11,535	34,639	33,748
Cash flow hedge gain expected to be reclassified from AOCI within 12 months			$ 475
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	(146)	(36)	$ (665)	103
Foreign exchange contracts
Pretax change in accumulated other comprehensive income (loss)
Total gain (loss) recognized in AOCI	(3)	(7)	(4)	(7)
Cash flow hedges \| (Gain) loss reclassified from AOCI
Pretax change in accumulated other comprehensive income (loss)
Other revenue	2	(55)	(8)	(102)
Net interest revenue	(54)		(142)
Cash flow hedges \| (Gain) loss reclassified from AOCI \| Interest rate contracts
Pretax change in accumulated other comprehensive income (loss)
Other revenue	0	(48)	0	(94)
Net interest revenue	(54)		(142)
Cash flow hedges \| (Gain) loss reclassified from AOCI \| Foreign exchange contracts
Pretax change in accumulated other comprehensive income (loss)
Other revenue	2	$ (7)	(8)	$ (8)
Net interest revenue	$ 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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- Definition

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

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