ALLOWANCE FOR CREDIT LOSSES - Allowance for Credit Losses Roll Forward (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of period	$ 18,216	$ 17,496	$ 18,145	$ 16,974
Gross credit losses on loans	(2,609)	(2,000)	(8,014)	(5,513)
Gross recoveries on loans	437	363	1,256	1,070
Net credit losses on loans (NCLs)	(2,172)	(1,637)	(6,758)	(4,443)
Net reserve builds (releases) for loans	254	100	636	787
Net specific reserve builds (releases) for loans	(44)	79	(231)	84
Total provision for credit losses on loans (PCLL)	2,382	1,816	7,163	5,314
Initial allowance for credit losses on newly purchased credit-deteriorated assets during the period(2)	23	0	23	0
Other, net (see table below)	(93)	(46)	(217)	136
ACLL at end of period	18,356	17,629	18,356	17,629
Allowance for credit losses on unfunded commitments
Allowance for credit losses on unfunded commitments (ACLUC) at beginning of period	1,619	1,862	1,728	2,151
Provision (release) for credit losses on unfunded lending commitments	105	(54)	(1)	(344)
Other, net	1	(2)	(2)	(1)
ACLUC at end of period	1,725	1,806	1,725	1,806
Total allowance for credit losses on loans, leases and unfunded lending commitments	20,081	19,435	20,081	19,435	$ 19,873
Sales or transfers of various consumer loan portfolios to HFS
FX translation and other	(93)	(46)	(217)	136
Other, net	(93)	(46)	(217)	136
Credit deteriorated assets, par value	37	6	46	19
Corporate loans
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of period	2,484	2,630	2,714	2,855
Gross credit losses on loans	(113)	(72)	(420)	(197)
Gross recoveries on loans	39	14	74	42
Net credit losses on loans (NCLs)	(74)	(58)	(346)	(155)
Net reserve builds (releases) for loans	143	25	115	(184)
Net specific reserve builds (releases) for loans	(40)	77	(229)	49
Initial allowance for credit losses on newly purchased credit-deteriorated assets during the period(2)	0	0	0	0
Other, net (see table below)	4	(15)	(9)	(3)
ACLL at end of period	2,591	2,717	2,591	2,717
Sales or transfers of various consumer loan portfolios to HFS
Other, net	4	(15)	(9)	(3)
Consumer loans
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of period	15,732	14,866	15,431	14,119
Gross credit losses on loans	(2,496)	(1,928)	(7,594)	(5,316)
Gross recoveries on loans	398	349	1,182	1,028
Net credit losses on loans (NCLs)	(2,098)	(1,579)	(6,412)	(4,288)
Net reserve builds (releases) for loans	111	75	521	971
Net specific reserve builds (releases) for loans	(4)	2	(2)	35
Initial allowance for credit losses on newly purchased credit-deteriorated assets during the period(2)	23	0	23	0
Other, net (see table below)	(97)	(31)	(208)	139
ACLL at end of period	15,765	14,912	15,765	14,912
Sales or transfers of various consumer loan portfolios to HFS
Other, net	(97)	(31)	(208)	139
Cumulative Effect, Period of Adoption, Adjustment
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of period				(352)
Cumulative Effect, Period of Adoption, Adjustment | Consumer loans
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of period				(352)
Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of period	$ 18,216	$ 17,496	18,145	16,622
Cumulative Effect, Period of Adoption, Adjusted Balance | Corporate loans
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of period			2,714	2,855
Cumulative Effect, Period of Adoption, Adjusted Balance | Consumer loans
Allowance for credit losses
Allowance for credit losses on loans (ACLL) at beginning of period			$ 15,431	$ 13,767