FAIR VALUE MEASUREMENT - Items Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Assets, Fair Value Disclosure [Abstract]
Federal funds sold and securities borrowed and purchased under agreements to resell, Netting	$ (235,024)	$ (112,391)
Trading account assets	406,368	334,114
Netting agreements	(333,991)	(346,545)
Netting of cash collateral received	(22,872)	(23,136)
Trading derivatives	68,554	75,306
Investments	508,998	526,582
Held at fair value	7,411	5,360
Liabilities, Fair Value Disclosure [Abstract]
Federal funds purchased and securities loaned and sold under agreements to repurchase, Netting	(235,024)	(112,391)
Netting agreements	(333,991)	(346,545)
Netting of cash collateral paid	(26,294)	(30,032)
Total derivative liabilities	54,761	59,916
Non-marketable equity securities | Carried at cost
Assets, Fair Value Disclosure [Abstract]
Investments	5,400	5,469
Fair Value Measured at Net Asset Value Per Share
Liabilities, Fair Value Disclosure [Abstract]
Investments measured at net asset value excluded from Level 3	24	27
Recurring
Assets, Fair Value Disclosure [Abstract]
Federal funds sold and securities borrowed and purchased under agreements to resell	440,450	350,294
Federal funds sold and securities borrowed and purchased under agreements to resell, Netting	(234,299)	(110,767)
Federal funds sold and securities borrowed and purchased under agreements to resell	206,151	239,527
Investments	242,497	250,547
Held at fair value	7,411	5,360
Mortgage servicing rights	729	665
Assets before netting	1,468,881	1,321,319
Netting, Assets, total of netting agreements and cash collateral received	(591,162)	(480,448)
Total assets	877,719	840,871
Liabilities, Fair Value Disclosure [Abstract]
Interest-bearing deposits	2,722	1,875
Federal funds purchased and securities loaned and sold under agreements to repurchase, Gross	226,186	156,853
Federal funds purchased and securities loaned and sold under agreements to repurchase, Netting	(165,524)	(85,967)
Federal funds purchased and securities loaned and sold under agreements to repurchase	60,662	70,886
Securities sold, not yet purchased	109,851	110,720
Trading liabilities	109,863	110,731
Short-term borrowings	6,470	6,222
Long-term debt	112,629	105,995
Total liabilities, Gross	880,232	822,608
Total liabilities, Netting	(525,809)	(462,544)
Total liabilities	354,423	360,064
Recurring | Trading account liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	415,046	436,493
Total trading derivatives and cash collateral, liability	415,046	436,493
Netting agreements	(333,991)	(346,545)
Netting of cash collateral paid	(26,294)	(30,032)
Netting, Liabilities, total of netting agreements and cash collateral received	(360,285)	(376,577)
Total derivative liabilities	54,761	59,916
Recurring | Trading account liabilities | Interest rate contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	173,259	172,620
Recurring | Trading account liabilities | Foreign exchange contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	166,951	185,995
Recurring | Trading account liabilities | Equity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	46,499	43,783
Recurring | Trading account liabilities | Commodity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	17,260	26,318
Recurring | Trading account liabilities | Credit derivatives
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	11,077	7,777
Recurring | Other financial liabilities measured on a recurring basis
Liabilities, Fair Value Disclosure [Abstract]
Netting of cash collateral paid		0
Netting, Liabilities, total of netting agreements and cash collateral received	0
Non-trading derivatives and other financial liabilities measured on a recurring basis, gross	7,316	4,439
Total other assets and cash collateral, gross	7,316	4,439
Recurring | Other trading liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	12	11
Recurring | Mortgage-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	71,067	38,409
Investments	20,123	11,749
Recurring | Mortgage securitizations - U.S. agency-sponsored
Assets, Fair Value Disclosure [Abstract]
Trading account assets	68,063	35,478
Investments	19,815	11,262
Recurring | Residential
Assets, Fair Value Disclosure [Abstract]
Trading account assets	2,294	1,988
Investments	307	485
Recurring | Commercial
Assets, Fair Value Disclosure [Abstract]
Trading account assets	710	943
Investments	1	2
Recurring | U.S. Treasury and federal agency securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	92,661	67,581
Investments	81,268	92,290
Recurring | State and municipal
Assets, Fair Value Disclosure [Abstract]
Trading account assets	1,906	2,263
Investments	2,031	2,223
Recurring | Foreign government
Assets, Fair Value Disclosure [Abstract]
Trading account assets	77,125	64,352
Investments	125,396	133,277
Recurring | Corporate
Assets, Fair Value Disclosure [Abstract]
Trading account assets	20,494	13,942
Investments	5,393	4,916
Recurring | Equity securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	57,380	54,361
Investments	283	429
Recurring | Asset-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	2,380	2,265
Investments	682	1,030
Recurring | Other debt securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	14,801	15,635
Investments	6,890	4,194
Recurring | Non-marketable equity securities
Assets, Fair Value Disclosure [Abstract]
Investments	431	439
Recurring | Trading non-derivative assets
Assets, Fair Value Disclosure [Abstract]
Trading account assets	337,814	258,808
Recurring | Trading account derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	425,417	444,987
Trading derivative, asset, gross net cash collateral paid	425,417	444,987
Netting agreements	(333,991)	(346,545)
Netting of cash collateral received	(22,872)	(23,136)
Total trading derivatives, netting	(356,863)	(369,681)
Trading derivatives	68,554	75,306
Recurring | Trading account derivatives | Interest rate contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	179,118	178,204
Recurring | Trading account derivatives | Foreign exchange contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	174,317	187,663
Recurring | Trading account derivatives | Equity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	43,053	42,407
Recurring | Trading account derivatives | Commodity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	16,287	28,324
Recurring | Trading account derivatives | Credit derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	12,642	8,389
Recurring | Non-trading derivatives and other financial assets measured on a recurring basis
Assets, Fair Value Disclosure [Abstract]
Total trading derivatives, netting	0	0
Total other assets and cash collateral, gross	14,563	10,658
Other assets	14,563	10,658
Recurring | Level 1
Assets, Fair Value Disclosure [Abstract]
Federal funds sold and securities borrowed and purchased under agreements to resell	0	0
Investments	141,940	152,754
Held at fair value	0	0
Mortgage servicing rights	0	0
Assets before netting	$ 333,338	$ 304,439
Total as a percentage of gross assets	22.70%	23.00%
Liabilities, Fair Value Disclosure [Abstract]
Interest-bearing deposits	$ 0	$ 0
Federal funds purchased and securities loaned and sold under agreements to repurchase, Gross	0	0
Securities sold, not yet purchased	96,351	97,559
Trading liabilities	96,351	97,559
Short-term borrowings	0	0
Long-term debt	0	0
Total liabilities, Gross	$ 103,617	$ 102,003
Total as a percentage of gross liabilities	11.80%	12.40%
Recurring | Level 1 | Trading account liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	$ 155	$ 247
Recurring | Level 1 | Trading account liabilities | Interest rate contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	120	175
Recurring | Level 1 | Trading account liabilities | Foreign exchange contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	0	0
Recurring | Level 1 | Trading account liabilities | Equity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	35	70
Recurring | Level 1 | Trading account liabilities | Commodity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	0	2
Recurring | Level 1 | Trading account liabilities | Credit derivatives
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	0	0
Recurring | Level 1 | Other financial liabilities measured on a recurring basis
Liabilities, Fair Value Disclosure [Abstract]
Other liabilities, gross	7,111	4,197
Recurring | Level 1 | Other trading liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	0	0
Recurring | Level 1 | Mortgage-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	1	1
Investments	0	0
Recurring | Level 1 | Mortgage securitizations - U.S. agency-sponsored
Assets, Fair Value Disclosure [Abstract]
Trading account assets	0	0
Investments	0	0
Recurring | Level 1 | Residential
Assets, Fair Value Disclosure [Abstract]
Trading account assets	1	1
Investments	0	0
Recurring | Level 1 | Commercial
Assets, Fair Value Disclosure [Abstract]
Trading account assets	0	0
Investments	0	0
Recurring | Level 1 | U.S. Treasury and federal agency securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	90,944	63,067
Investments	80,949	91,851
Recurring | Level 1 | State and municipal
Assets, Fair Value Disclosure [Abstract]
Trading account assets	0	0
Investments	0	0
Recurring | Level 1 | Foreign government
Assets, Fair Value Disclosure [Abstract]
Trading account assets	45,369	38,383
Investments	57,970	58,419
Recurring | Level 1 | Corporate
Assets, Fair Value Disclosure [Abstract]
Trading account assets	1,363	1,593
Investments	2,835	2,230
Recurring | Level 1 | Equity securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	46,513	43,990
Investments	186	254
Recurring | Level 1 | Asset-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	0	0
Investments	0	0
Recurring | Level 1 | Other debt securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	64	24
Investments	0	0
Recurring | Level 1 | Non-marketable equity securities
Assets, Fair Value Disclosure [Abstract]
Investments	0	0
Recurring | Level 1 | Trading non-derivative assets
Assets, Fair Value Disclosure [Abstract]
Trading account assets	184,254	147,058
Recurring | Level 1 | Trading account derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	154	317
Recurring | Level 1 | Trading account derivatives | Interest rate contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	129	297
Recurring | Level 1 | Trading account derivatives | Foreign exchange contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	0	0
Recurring | Level 1 | Trading account derivatives | Equity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	25	20
Recurring | Level 1 | Trading account derivatives | Commodity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	0	0
Recurring | Level 1 | Trading account derivatives | Credit derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	0	0
Recurring | Level 1 | Non-trading derivatives and other financial assets measured on a recurring basis
Assets, Fair Value Disclosure [Abstract]
Other assets, gross	6,990	4,310
Recurring | Level 2
Assets, Fair Value Disclosure [Abstract]
Federal funds sold and securities borrowed and purchased under agreements to resell	440,315	350,145
Investments	99,034	95,744
Held at fair value	7,146	3,999
Mortgage servicing rights	0	0
Assets before netting	$ 1,121,758	$ 1,001,032
Total as a percentage of gross assets	76.40%	75.80%
Liabilities, Fair Value Disclosure [Abstract]
Interest-bearing deposits	$ 2,567	$ 1,860
Federal funds purchased and securities loaned and sold under agreements to repurchase, Gross	225,705	155,822
Securities sold, not yet purchased	13,412	13,111
Trading liabilities	13,423	13,119
Short-term borrowings	6,014	6,184
Long-term debt	76,979	69,878
Total liabilities, Gross	$ 730,052	$ 674,144
Total as a percentage of gross liabilities	82.90%	82.00%
Recurring | Level 2 | Trading account liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	$ 405,187	$ 427,041
Recurring | Level 2 | Trading account liabilities | Interest rate contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	168,590	169,049
Recurring | Level 2 | Trading account liabilities | Foreign exchange contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	166,133	185,279
Recurring | Level 2 | Trading account liabilities | Equity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	44,118	40,905
Recurring | Level 2 | Trading account liabilities | Commodity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	16,035	25,093
Recurring | Level 2 | Trading account liabilities | Credit derivatives
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	10,311	6,715
Recurring | Level 2 | Other financial liabilities measured on a recurring basis
Liabilities, Fair Value Disclosure [Abstract]
Other liabilities, gross	177	240
Recurring | Level 2 | Other trading liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	11	8
Recurring | Level 2 | Mortgage-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	70,158	37,497
Investments	20,070	11,678
Recurring | Level 2 | Mortgage securitizations - U.S. agency-sponsored
Assets, Fair Value Disclosure [Abstract]
Trading account assets	67,525	34,878
Investments	19,786	11,232
Recurring | Level 2 | Residential
Assets, Fair Value Disclosure [Abstract]
Trading account assets	2,128	1,821
Investments	283	444
Recurring | Level 2 | Commercial
Assets, Fair Value Disclosure [Abstract]
Trading account assets	505	798
Investments	1	2
Recurring | Level 2 | U.S. Treasury and federal agency securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	1,717	4,513
Investments	299	439
Recurring | Level 2 | State and municipal
Assets, Fair Value Disclosure [Abstract]
Trading account assets	1,903	2,256
Investments	1,538	1,637
Recurring | Level 2 | Foreign government
Assets, Fair Value Disclosure [Abstract]
Trading account assets	31,687	25,850
Investments	67,230	74,250
Recurring | Level 2 | Corporate
Assets, Fair Value Disclosure [Abstract]
Trading account assets	18,367	11,955
Investments	2,269	2,343
Recurring | Level 2 | Equity securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	10,604	10,179
Investments	86	165
Recurring | Level 2 | Asset-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	1,805	1,597
Investments	652	1,029
Recurring | Level 2 | Other debt securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	13,764	14,963
Investments	6,890	4,194
Recurring | Level 2 | Non-marketable equity securities
Assets, Fair Value Disclosure [Abstract]
Investments	0	9
Recurring | Level 2 | Trading non-derivative assets
Assets, Fair Value Disclosure [Abstract]
Trading account assets	150,005	108,810
Recurring | Level 2 | Trading account derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	417,762	436,043
Recurring | Level 2 | Trading account derivatives | Interest rate contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	176,243	174,156
Recurring | Level 2 | Trading account derivatives | Foreign exchange contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	172,886	186,897
Recurring | Level 2 | Trading account derivatives | Equity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	41,817	40,683
Recurring | Level 2 | Trading account derivatives | Commodity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	15,013	26,823
Recurring | Level 2 | Trading account derivatives | Credit derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	11,803	7,484
Recurring | Level 2 | Non-trading derivatives and other financial assets measured on a recurring basis
Assets, Fair Value Disclosure [Abstract]
Other assets, gross	7,496	6,291
Recurring | Level 3
Assets, Fair Value Disclosure [Abstract]
Federal funds sold and securities borrowed and purchased under agreements to resell	135	149
Investments	1,523	2,049
Held at fair value	265	1,361
Mortgage servicing rights	729	665
Assets before netting	$ 13,785	$ 15,848
Total as a percentage of gross assets	0.90%	1.20%
Liabilities, Fair Value Disclosure [Abstract]
Interest-bearing deposits	$ 155	$ 15
Federal funds purchased and securities loaned and sold under agreements to repurchase, Gross	481	1,031
Securities sold, not yet purchased	88	50
Trading liabilities	89	53
Short-term borrowings	456	38
Long-term debt	35,650	36,117
Total liabilities, Gross	$ 46,563	$ 46,461
Total as a percentage of gross liabilities	5.30%	5.60%
Recurring | Level 3 | Trading account liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	$ 9,704	$ 9,205
Recurring | Level 3 | Trading account liabilities | Interest rate contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	4,549	3,396
Recurring | Level 3 | Trading account liabilities | Foreign exchange contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	818	716
Recurring | Level 3 | Trading account liabilities | Equity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	2,346	2,808
Recurring | Level 3 | Trading account liabilities | Commodity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	1,225	1,223
Recurring | Level 3 | Trading account liabilities | Credit derivatives
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	766	1,062
Recurring | Level 3 | Other financial liabilities measured on a recurring basis
Liabilities, Fair Value Disclosure [Abstract]
Other liabilities, gross	28	2
Recurring | Level 3 | Other trading liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	1	3
Recurring | Level 3 | Mortgage-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	908	911
Investments	53	71
Recurring | Level 3 | Mortgage securitizations - U.S. agency-sponsored
Assets, Fair Value Disclosure [Abstract]
Trading account assets	538	600
Investments	29	30
Recurring | Level 3 | Residential
Assets, Fair Value Disclosure [Abstract]
Trading account assets	165	166
Investments	24	41
Recurring | Level 3 | Commercial
Assets, Fair Value Disclosure [Abstract]
Trading account assets	205	145
Investments	0	0
Recurring | Level 3 | U.S. Treasury and federal agency securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	0	1
Investments	20	0
Recurring | Level 3 | State and municipal
Assets, Fair Value Disclosure [Abstract]
Trading account assets	3	7
Investments	493	586
Recurring | Level 3 | Foreign government
Assets, Fair Value Disclosure [Abstract]
Trading account assets	69	119
Investments	196	608
Recurring | Level 3 | Corporate
Assets, Fair Value Disclosure [Abstract]
Trading account assets	764	394
Investments	289	343
Recurring | Level 3 | Equity securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	263	192
Investments	11	10
Recurring | Level 3 | Asset-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	575	668
Investments	30	1
Recurring | Level 3 | Other debt securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	973	648
Investments	0	0
Recurring | Level 3 | Non-marketable equity securities
Assets, Fair Value Disclosure [Abstract]
Investments	431	430
Recurring | Level 3 | Trading non-derivative assets
Assets, Fair Value Disclosure [Abstract]
Trading account assets	3,555	2,940
Recurring | Level 3 | Trading account derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	7,501	8,627
Recurring | Level 3 | Trading account derivatives | Interest rate contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	2,746	3,751
Recurring | Level 3 | Trading account derivatives | Foreign exchange contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	1,431	766
Recurring | Level 3 | Trading account derivatives | Equity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	1,211	1,704
Recurring | Level 3 | Trading account derivatives | Commodity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	1,274	1,501
Recurring | Level 3 | Trading account derivatives | Credit derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	839	905
Recurring | Level 3 | Non-trading derivatives and other financial assets measured on a recurring basis
Assets, Fair Value Disclosure [Abstract]
Other assets, gross	$ 77	$ 57