FAIR VALUE MEASUREMENT - Items Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Assets, Fair Value Disclosure [Abstract]
Federal funds sold and securities borrowed and purchased under agreements to resell, Netting	$ (273,081)	$ (248,214)
Trading account assets	446,339	411,756
Netting agreements	(277,223)	(308,431)
Netting of cash collateral received	(25,575)	(21,226)
Trading derivatives	53,064	57,717
Investments	508,276	519,085
Held at fair value	8,526	7,594
Liabilities, Fair Value Disclosure [Abstract]
Federal funds purchased and securities loaned and sold under agreements to repurchase, Netting	(273,081)	(248,214)
Netting agreements	(277,223)	(308,431)
Netting of cash collateral paid	(28,644)	(26,101)
Total derivative liabilities	47,072	50,679
Marketable equity securities carried at fair value	165	258
Non-marketable equity securities | Carried at cost
Assets, Fair Value Disclosure [Abstract]
Investments	5,400	5,500
Fair Value Measured at Net Asset Value Per Share
Liabilities, Fair Value Disclosure [Abstract]
Investments measured at net asset value excluded from Level 3	26	25
Recurring
Assets, Fair Value Disclosure [Abstract]
Federal funds sold and securities borrowed and purchased under agreements to resell	450,112	453,854
Federal funds sold and securities borrowed and purchased under agreements to resell, Netting	(272,050)	(247,795)
Federal funds sold and securities borrowed and purchased under agreements to resell	178,062	206,059
Investments	250,032	257,677
Held at fair value	8,526	7,594
Mortgage servicing rights	709	691
Assets before netting	1,474,355	1,474,257
Netting, Assets, total of netting agreements and cash collateral received	(574,848)	(577,452)
Total assets	899,507	896,805
Liabilities, Fair Value Disclosure [Abstract]
Interest-bearing deposits	3,400	2,440
Federal funds purchased and securities loaned and sold under agreements to repurchase, Gross	260,306	228,438
Federal funds purchased and securities loaned and sold under agreements to repurchase, Netting	(190,538)	(165,953)
Federal funds purchased and securities loaned and sold under agreements to repurchase	69,768	62,485
Securities sold, not yet purchased	104,176	104,658
Trading liabilities	104,187	104,666
Short-term borrowings	11,744	6,545
Long-term debt	109,406	116,338
Total liabilities, Gross	847,367	848,072
Total liabilities, Netting	(496,405)	(500,485)
Total liabilities	350,962	347,587
Recurring | Trading account liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	352,939	385,211
Total trading derivatives and cash collateral, liability	352,939	385,211
Netting agreements	(277,223)	(308,431)
Netting of cash collateral paid	(28,644)	(26,101)
Netting, Liabilities, total of netting agreements and cash collateral received	(305,867)	(334,532)
Total derivative liabilities	47,072	50,679
Recurring | Trading account liabilities | Interest rate contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	135,787	153,186
Recurring | Trading account liabilities | Foreign exchange contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	129,590	157,201
Recurring | Trading account liabilities | Equity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	64,444	47,946
Recurring | Trading account liabilities | Commodity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	15,388	18,796
Recurring | Trading account liabilities | Credit derivatives
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	7,730	8,082
Recurring | Other financial liabilities
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	5,385	4,434
Total other assets and cash collateral, gross	5,385	4,434
Recurring | Other trading liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	11	8
Recurring | Mortgage-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	83,134	81,756
Investments	32,359	30,139
Recurring | Mortgage securitizations - U.S. agency-sponsored
Assets, Fair Value Disclosure [Abstract]
Trading account assets	81,340	80,376
Investments	31,770	29,715
Recurring | Residential
Assets, Fair Value Disclosure [Abstract]
Trading account assets	651	714
Investments	588	423
Recurring | Commercial Mortgage-Backed Securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	1,143	666
Investments	1	1
Recurring | U.S. Treasury and federal agency securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	110,742	115,256
Investments	69,632	80,361
Recurring | State and municipal
Assets, Fair Value Disclosure [Abstract]
Trading account assets	212	597
Investments	1,889	2,131
Recurring | Foreign government
Assets, Fair Value Disclosure [Abstract]
Trading account assets	90,556	72,495
Investments	134,099	131,198
Recurring | Corporate
Assets, Fair Value Disclosure [Abstract]
Trading account assets	23,340	19,074
Investments	5,302	5,412
Recurring | Equity securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	64,774	45,393
Investments	165	258
Recurring | Asset-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	1,755	1,754
Investments	768	938
Recurring | Other debt securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	18,762	17,714
Investments	5,313	6,757
Recurring | Non-marketable equity securities
Assets, Fair Value Disclosure [Abstract]
Investments	505	483
Recurring | Trading non-derivative assets
Assets, Fair Value Disclosure [Abstract]
Trading account assets	393,275	354,039
Recurring | Trading account derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	355,862	387,374
Trading derivative, asset, gross net cash collateral paid	355,862	387,374
Netting agreements	(277,223)	(308,431)
Netting of cash collateral received	(25,575)	(21,226)
Total trading derivatives, netting	(302,798)	(329,657)
Trading derivatives	53,064	57,717
Recurring | Trading account derivatives | Interest rate contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	144,066	158,494
Recurring | Trading account derivatives | Foreign exchange contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	137,917	159,694
Recurring | Trading account derivatives | Equity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	52,378	43,278
Recurring | Trading account derivatives | Commodity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	13,358	17,569
Recurring | Trading account derivatives | Credit derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	8,143	8,339
Recurring | Other financial assets
Assets, Fair Value Disclosure [Abstract]
Total trading derivatives, netting	0	0
Total other assets and cash collateral, gross	15,839	13,028
Other assets	15,839	13,028
Recurring | Level 1
Assets, Fair Value Disclosure [Abstract]
Federal funds sold and securities borrowed and purchased under agreements to resell	1,527	0
Investments	135,174	143,034
Held at fair value	0	0
Mortgage servicing rights	0	0
Assets before netting	$ 364,542	$ 339,746
Total as a percentage of gross assets	24.70%	23.00%
Liabilities, Fair Value Disclosure [Abstract]
Interest-bearing deposits	$ 82	$ 0
Federal funds purchased and securities loaned and sold under agreements to repurchase, Gross	254	0
Securities sold, not yet purchased	88,480	91,163
Trading liabilities	88,480	91,163
Short-term borrowings	0	0
Long-term debt	0	0
Total liabilities, Gross	$ 93,607	$ 95,528
Total as a percentage of gross liabilities	11.00%	11.30%
Recurring | Level 1 | Trading account liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	$ 131	$ 67
Recurring | Level 1 | Trading account liabilities | Interest rate contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	61	49
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	70	18
Recurring | Level 1 | Trading account liabilities | Commodity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	0	0
Recurring | Level 1 | Trading account liabilities | Credit derivatives
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	0	0
Recurring | Level 1 | Other financial liabilities
Liabilities, Fair Value Disclosure [Abstract]
Other liabilities, gross	4,660	4,298
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	0	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	0	1
Investments	0	0
Recurring | Level 1 | Commercial Mortgage-Backed Securities
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	109,422	112,851
Investments	69,632	80,062
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	54,488	44,203
Investments	62,192	60,133
Recurring | Level 1 | Corporate
Assets, Fair Value Disclosure [Abstract]
Trading account assets	1,467	1,858
Investments	3,208	2,680
Recurring | Level 1 | Equity securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	56,150	32,966
Investments	142	159
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	602	97
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	222,129	191,976
Recurring | Level 1 | Trading account derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	123	59
Recurring | Level 1 | Trading account derivatives | Interest rate contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	57	49
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	66	8
Recurring | Level 1 | Trading account derivatives | Commodity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	0	2
Recurring | Level 1 | Trading account derivatives | Credit derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	0	0
Recurring | Level 1 | Other financial assets
Assets, Fair Value Disclosure [Abstract]
Other assets, gross	5,589	4,677
Recurring | Level 2
Assets, Fair Value Disclosure [Abstract]
Federal funds sold and securities borrowed and purchased under agreements to resell	448,459	453,715
Investments	113,725	112,844
Held at fair value	8,225	7,167
Mortgage servicing rights	0	0
Assets before netting	$ 1,098,244	$ 1,121,860
Total as a percentage of gross assets	74.50%	76.10%
Liabilities, Fair Value Disclosure [Abstract]
Interest-bearing deposits	$ 3,277	$ 2,411
Federal funds purchased and securities loaned and sold under agreements to repurchase, Gross	259,766	228,048
Securities sold, not yet purchased	15,664	13,460
Trading liabilities	15,675	13,468
Short-term borrowings	11,543	6,064
Long-term debt	89,031	77,958
Total liabilities, Gross	$ 724,074	$ 704,559
Total as a percentage of gross liabilities	85.50%	83.00%
Recurring | Level 2 | Trading account liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	$ 344,060	$ 376,480
Recurring | Level 2 | Trading account liabilities | Interest rate contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	132,231	149,914
Recurring | Level 2 | Trading account liabilities | Foreign exchange contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	128,944	156,474
Recurring | Level 2 | Trading account liabilities | Equity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	61,341	44,894
Recurring | Level 2 | Trading account liabilities | Commodity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	14,624	17,964
Recurring | Level 2 | Trading account liabilities | Credit derivatives
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	6,920	7,234
Recurring | Level 2 | Other financial liabilities
Liabilities, Fair Value Disclosure [Abstract]
Other liabilities, gross	722	130
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	82,186	80,856
Investments	32,306	29,948
Recurring | Level 2 | Mortgage securitizations - U.S. agency-sponsored
Assets, Fair Value Disclosure [Abstract]
Trading account assets	80,649	79,795
Investments	31,742	29,640
Recurring | Level 2 | Residential
Assets, Fair Value Disclosure [Abstract]
Trading account assets	560	597
Investments	563	307
Recurring | Level 2 | Commercial Mortgage-Backed Securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	977	464
Investments	1	1
Recurring | Level 2 | U.S. Treasury and federal agency securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	1,320	2,398
Investments	0	299
Recurring | Level 2 | State and municipal
Assets, Fair Value Disclosure [Abstract]
Trading account assets	211	594
Investments	1,450	1,589
Recurring | Level 2 | Foreign government
Assets, Fair Value Disclosure [Abstract]
Trading account assets	36,023	28,238
Investments	71,893	70,871
Recurring | Level 2 | Corporate
Assets, Fair Value Disclosure [Abstract]
Trading account assets	21,558	16,716
Investments	1,982	2,370
Recurring | Level 2 | Equity securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	8,380	12,135
Investments	13	72
Recurring | Level 2 | Equity Securities Subject To Contractual Sale Restriction
Liabilities, Fair Value Disclosure [Abstract]
Marketable equity securities carried at fair value	2,200
Recurring | Level 2 | Asset-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	1,511	1,223
Investments	768	938
Recurring | Level 2 | Other debt securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	17,377	16,784
Investments	5,313	6,757
Recurring | Level 2 | Non-marketable equity securities
Assets, Fair Value Disclosure [Abstract]
Investments	0	0
Recurring | Level 2 | Trading non-derivative assets
Assets, Fair Value Disclosure [Abstract]
Trading account assets	168,566	158,944
Recurring | Level 2 | Trading account derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	349,040	380,869
Recurring | Level 2 | Trading account derivatives | Interest rate contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	141,542	156,307
Recurring | Level 2 | Trading account derivatives | Foreign exchange contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	136,720	158,672
Recurring | Level 2 | Trading account derivatives | Equity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	51,329	41,870
Recurring | Level 2 | Trading account derivatives | Commodity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	12,190	16,456
Recurring | Level 2 | Trading account derivatives | Credit derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	7,259	7,564
Recurring | Level 2 | Other financial assets
Assets, Fair Value Disclosure [Abstract]
Other assets, gross	10,229	8,321
Recurring | Level 3
Assets, Fair Value Disclosure [Abstract]
Federal funds sold and securities borrowed and purchased under agreements to resell	126	139
Investments	1,133	1,799
Held at fair value	301	427
Mortgage servicing rights	709	691
Assets before netting	$ 11,569	$ 12,651
Total as a percentage of gross assets	0.80%	0.90%
Liabilities, Fair Value Disclosure [Abstract]
Interest-bearing deposits	$ 41	$ 29
Federal funds purchased and securities loaned and sold under agreements to repurchase, Gross	286	390
Securities sold, not yet purchased	32	35
Trading liabilities	32	35
Short-term borrowings	201	481
Long-term debt	20,375	38,380
Total liabilities, Gross	$ 29,686	$ 47,985
Total as a percentage of gross liabilities	3.50%	5.70%
Recurring | Level 3 | Trading account liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	$ 8,748	$ 8,664
Recurring | Level 3 | Trading account liabilities | Interest rate contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	3,495	3,223
Recurring | Level 3 | Trading account liabilities | Foreign exchange contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	646	727
Recurring | Level 3 | Trading account liabilities | Equity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	3,033	3,034
Recurring | Level 3 | Trading account liabilities | Commodity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	764	832
Recurring | Level 3 | Trading account liabilities | Credit derivatives
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	810	848
Recurring | Level 3 | Other financial liabilities
Liabilities, Fair Value Disclosure [Abstract]
Other liabilities, gross	3	6
Recurring | Level 3 | Other trading liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	0	0
Recurring | Level 3 | Mortgage-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	948	899
Investments	53	191
Recurring | Level 3 | Mortgage securitizations - U.S. agency-sponsored
Assets, Fair Value Disclosure [Abstract]
Trading account assets	691	581
Investments	28	75
Recurring | Level 3 | Residential
Assets, Fair Value Disclosure [Abstract]
Trading account assets	91	116
Investments	25	116
Recurring | Level 3 | Commercial Mortgage-Backed Securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	166	202
Investments	0	0
Recurring | Level 3 | U.S. Treasury and federal agency securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	0	7
Investments	0	0
Recurring | Level 3 | State and municipal
Assets, Fair Value Disclosure [Abstract]
Trading account assets	1	3
Investments	439	542
Recurring | Level 3 | Foreign government
Assets, Fair Value Disclosure [Abstract]
Trading account assets	45	54
Investments	14	194
Recurring | Level 3 | Corporate
Assets, Fair Value Disclosure [Abstract]
Trading account assets	315	500
Investments	112	362
Recurring | Level 3 | Equity securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	244	292
Investments	10	27
Recurring | Level 3 | Asset-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	244	531
Investments	0	0
Recurring | Level 3 | Other debt securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	783	833
Investments	0	0
Recurring | Level 3 | Non-marketable equity securities
Assets, Fair Value Disclosure [Abstract]
Investments	505	483
Recurring | Level 3 | Trading non-derivative assets
Assets, Fair Value Disclosure [Abstract]
Trading account assets	2,580	3,119
Recurring | Level 3 | Trading account derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	6,699	6,446
Recurring | Level 3 | Trading account derivatives | Interest rate contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	2,467	2,138
Recurring | Level 3 | Trading account derivatives | Foreign exchange contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	1,197	1,022
Recurring | Level 3 | Trading account derivatives | Equity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	983	1,400
Recurring | Level 3 | Trading account derivatives | Commodity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	1,168	1,111
Recurring | Level 3 | Trading account derivatives | Credit derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	884	775
Recurring | Level 3 | Other financial assets
Assets, Fair Value Disclosure [Abstract]
Other assets, gross	$ 21	$ 30