ALLOWANCE FOR CREDIT LOSSES - Allowance for Credit Losses Roll Forward (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of period	$ 17,496	$ 15,952	$ 16,974	$ 16,455
Gross credit losses on loans	(2,000)	(1,237)	(5,513)	(3,689)
Gross recoveries on loans	363	350	1,070	1,080
Net credit losses on loans (NCLs)	(1,637)	(887)	(4,443)	(2,609)
Net reserve builds (releases) for loans	100	519	787	259
Net specific reserve builds (releases) for loans	79	(78)	84	104
Total provision for credit losses on loans (PCLL)	1,816	1,328	5,314	2,972
Other, net (see table below)	(46)	(84)	136	(509)
ACLL at end of period	17,629	16,309	17,629	16,309
Allowance for credit losses on unfunded commitments
Allowance for credit losses on unfunded commitments (ACLUC) at beginning of period	1,862	2,193	2,151	1,871
Provision (release) for credit losses on unfunded lending commitments	(54)	(71)	(344)	244
Other, net	(2)	(33)	(1)	(26)
ACLUC at end of period	1,806	2,089	1,806	2,089
Total allowance for credit losses on loans, leases and unfunded lending commitments	19,435	18,398	19,435	18,398	$ 19,125
Sales or transfers of various consumer loan portfolios to HFS
Reclasses of consumer ACLL to HFS	0	0	0	(350)
FX translation and other	(46)	(84)	136	(159)
Other, net	(46)	(84)	136	(509)
Cumulative Effect, Period of Adoption, Adjustment
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of period	0	0	(352)	0
Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of period	$ 17,496	$ 15,952	$ 16,622	$ 16,455

Financing Receivable, Allowance For Credit Losses, Unfunded Lending Commitments [Roll Forward]

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The reserve to cover probable credit losses related to financing receivable and unfunded lending commitments as of the balance sheet date.

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Financing Receivable, Excluding Accrued Interest, Allowance For Credit Loss, Adjustments, Other

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Provision charged or released during the period against earnings for credit losses on loans and leases receivable that are expected and were collectively evaluated for impairment.

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Provision charged or released during the period against earnings for credit losses on loans and leases receivable that are expected and were individually evaluated for impairment.

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Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease.

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Amount, excluding accrued interest, of foreign currency translation gain (loss) which decreases (increases) allowance for credit loss on financing receivable. Excludes net investment in lease.

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Amount, excluding accrued interest, of increase in allowance for credit loss on financing receivable from recovery. Excludes net investment in lease.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount, excluding accrued interest, of decrease in allowance for credit loss on financing receivable from writeoff. Excludes net investment in lease.

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Amount, excluding accrued interest, of decrease (increase) in allowance for credit loss on financing receivable from writeoff (recovery). Excludes net investment in lease.

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Amount, excluding accrued interest, of credit loss expense (reversal of expense) on financing receivable. Excludes net investment in lease.

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Amount, excluding accrued interest, of reversal of credit loss expense on financing receivable transferred out of held-for-investment into held-for-sale classification. Excludes net investment in lease.

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Amount of expected credit loss for credit exposure on off-balance-sheet commitment, including but not limited to, loan commitment, standby letter of credit, financial guarantee not accounted for as insurance. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

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Amount of expense (reversal of expense) for expected credit loss for off-balance sheet credit exposure. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

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