FAIR VALUE MEASUREMENT - Items Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Assets, Fair Value Disclosure [Abstract]
Federal funds sold and securities borrowed and purchased under agreements to resell, Netting	$ (99,999)	$ (131,342)
Trading account assets	340,875	331,945
Netting agreements	(348,255)	(292,628)
Netting of cash collateral received	(32,563)	(24,447)
Trading derivatives	81,885	69,776
Investments	513,878	512,822
Loans held at fair value	4,536	6,082
Liabilities, Fair Value Disclosure [Abstract]
Federal funds purchased and securities loaned and sold under agreements to repurchase, Netting	(99,999)	(131,342)
Netting agreements	(348,255)	(292,628)
Netting of cash collateral paid	(33,950)	(29,306)
Total derivative liabilities	62,757	55,516
Fair value
Liabilities, Fair Value Disclosure [Abstract]
Investments measured at net asset value excluded from Level 3	141	145
Recurring
Assets, Fair Value Disclosure [Abstract]
Federal funds sold and securities borrowed and purchased under agreements to resell	341,017	342,261
Federal funds sold and securities borrowed and purchased under agreements to resell, Netting	(98,257)	(125,795)
Federal funds sold and securities borrowed and purchased under agreements to resell	242,760	216,466
Investments	239,404	289,409
Loans held at fair value	4,536	6,082
Mortgage servicing rights	600	404
Assets before netting	1,317,335	1,299,518
Netting, Assets, total of netting agreements and cash collateral received	(479,075)	(442,870)
Total assets	838,260	856,648
Liabilities, Fair Value Disclosure [Abstract]
Interest-bearing deposits	2,308	1,666
Federal funds purchased and securities loaned and sold under agreements to repurchase, Gross	155,350	174,961
Federal funds purchased and securities loaned and sold under agreements to repurchase, Netting	(90,776)	(118,267)
Federal funds purchased and securities loaned and sold under agreements to repurchase	64,574	56,694
Securities sold, not yet purchased	117,692	106,008
Trading liabilities	117,696	106,013
Short-term borrowings	6,852	7,358
Long-term debt	89,388	82,609
Total liabilities, Gross	819,844	753,632
Total liabilities, Netting	(472,981)	(440,201)
Total liabilities	346,863	313,431
Recurring | Trading account liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	444,962	377,450
Total trading derivatives and cash collateral, liability	444,962	377,450
Netting agreements	(348,255)	(292,628)
Netting of cash collateral paid	(33,950)	(29,306)
Netting, Liabilities, total of netting agreements and cash collateral received	(382,205)	(321,934)
Total derivative liabilities	62,757	55,516
Recurring | Trading account liabilities | Interest rate contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	150,137	150,074
Recurring | Trading account liabilities | Foreign exchange contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	181,392	135,298
Recurring | Trading account liabilities | Equity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	58,509	49,684
Recurring | Trading account liabilities | Commodity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	44,629	31,379
Recurring | Trading account liabilities | Credit derivatives
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	10,295	11,015
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	3,288	3,575
Total other assets and cash collateral, gross	3,288	3,575
Recurring | Other trading liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	4	5
Recurring | Mortgage-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	34,499	36,637
Investments	12,800	33,621
Recurring | Mortgage securitizations - U.S. agency-sponsored
Assets, Fair Value Disclosure [Abstract]
Trading account assets	32,829	35,030
Investments	12,515	33,216
Recurring | Residential
Assets, Fair Value Disclosure [Abstract]
Trading account assets	672	748
Investments	278	380
Recurring | Commercial
Assets, Fair Value Disclosure [Abstract]
Trading account assets	998	859
Investments	7	25
Recurring | U.S. Treasury and federal agency securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	60,909	48,134
Investments	91,864	122,440
Recurring | State and municipal
Assets, Fair Value Disclosure [Abstract]
Trading account assets	1,761	2,032
Investments	2,492	2,621
Recurring | Foreign government
Assets, Fair Value Disclosure [Abstract]
Trading account assets	70,652	70,684
Investments	119,686	118,740
Recurring | Corporate
Assets, Fair Value Disclosure [Abstract]
Trading account assets	17,529	18,112
Investments	6,445	5,920
Recurring | Equity securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	51,271	64,054
Investments	588	543
Recurring | Asset-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	1,958	1,594
Investments	276	303
Recurring | Other trading assets
Assets, Fair Value Disclosure [Abstract]
Trading account assets	20,411	20,922
Investments	4,936	4,877
Recurring | Non-marketable equity securities
Assets, Fair Value Disclosure [Abstract]
Investments	317	344
Recurring | Trading non-derivative assets
Assets, Fair Value Disclosure [Abstract]
Trading account assets	258,990	262,169
Recurring | Trading account derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	462,703	386,851
Trading derivative, asset, gross net cash collateral paid	462,703	386,851
Netting agreements	(348,255)	(292,628)
Netting of cash collateral received	(32,563)	(24,447)
Total trading derivatives, netting	(380,818)	(317,075)
Trading derivatives	81,885	69,776
Recurring | Trading account derivatives | Interest rate contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	159,525	165,488
Recurring | Trading account derivatives | Foreign exchange contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	186,110	135,549
Recurring | Trading account derivatives | Equity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	55,591	45,252
Recurring | Trading account derivatives | Commodity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	49,676	30,344
Recurring | Trading account derivatives | Credit derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	11,801	10,218
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	10,085	12,342
Other assets	10,085	12,342
Recurring | Level 1
Assets, Fair Value Disclosure [Abstract]
Federal funds sold and securities borrowed and purchased under agreements to resell	0	0
Investments	146,246	182,324
Loans held at fair value	0	0
Mortgage servicing rights	0	0
Assets before netting	$ 295,480	$ 325,984
Total as a percentage of gross assets	22.40%	25.10%
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	98,389	82,675
Trading liabilities	98,389	82,675
Short-term borrowings	0	0
Long-term debt	0	0
Total liabilities, Gross	$ 102,132	$ 86,365
Total as a percentage of gross liabilities	12.50%	11.50%
Recurring | Level 1 | Trading account liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	$ 455	$ 116
Recurring | Level 1 | Trading account liabilities | Interest rate contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	347	56
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	108	60
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 measured on a recurring basis
Liabilities, Fair Value Disclosure [Abstract]
Other liabilities, gross	3,288	3,574
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
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	56,991	44,900
Investments	91,530	122,271
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	43,585	39,176
Investments	51,472	56,842
Recurring | Level 1 | Corporate
Assets, Fair Value Disclosure [Abstract]
Trading account assets	2,415	1,544
Investments	2,838	2,861
Recurring | Level 1 | Equity securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	42,192	53,833
Investments	406	350
Recurring | Level 1 | Asset-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	0	0
Investments	0	0
Recurring | Level 1 | Other trading assets
Assets, Fair Value Disclosure [Abstract]
Trading account assets	18	0
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	145,201	139,454
Recurring | Level 1 | Trading account derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	531	131
Recurring | Level 1 | Trading account derivatives | Interest rate contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	476	90
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	55	41
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	3,502	4,075
Recurring | Level 2
Assets, Fair Value Disclosure [Abstract]
Federal funds sold and securities borrowed and purchased under agreements to resell	340,834	342,030
Investments	90,895	104,858
Loans held at fair value	4,211	5,371
Mortgage servicing rights	0	0
Assets before netting	$ 1,004,932	$ 958,810
Total as a percentage of gross assets	76.30%	73.80%
Liabilities, Fair Value Disclosure [Abstract]
Interest-bearing deposits	$ 2,290	$ 1,483
Federal funds purchased and securities loaned and sold under agreements to repurchase, Gross	154,757	174,318
Securities sold, not yet purchased	19,231	23,268
Trading liabilities	19,235	23,273
Short-term borrowings	6,771	7,253
Long-term debt	59,610	57,100
Total liabilities, Gross	$ 678,007	$ 632,091
Total as a percentage of gross liabilities	82.70%	83.90%
Recurring | Level 2 | Trading account liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	$ 435,344	$ 368,664
Recurring | Level 2 | Trading account liabilities | Interest rate contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	147,534	147,846
Recurring | Level 2 | Trading account liabilities | Foreign exchange contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	180,531	134,572
Recurring | Level 2 | Trading account liabilities | Equity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	56,115	46,177
Recurring | Level 2 | Trading account liabilities | Commodity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	42,461	30,004
Recurring | Level 2 | Trading account liabilities | Credit derivatives
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	8,703	10,065
Recurring | Level 2 | Other financial liabilities measured on a recurring basis
Liabilities, Fair Value Disclosure [Abstract]
Other liabilities, gross	0	0
Recurring | Level 2 | Other trading liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	4	5
Recurring | Level 2 | Mortgage-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	33,500	35,955
Investments	12,732	33,476
Recurring | Level 2 | Mortgage securitizations - U.S. agency-sponsored
Assets, Fair Value Disclosure [Abstract]
Trading account assets	32,121	34,534
Investments	12,487	33,165
Recurring | Level 2 | Residential
Assets, Fair Value Disclosure [Abstract]
Trading account assets	519	643
Investments	238	286
Recurring | Level 2 | Commercial
Assets, Fair Value Disclosure [Abstract]
Trading account assets	860	778
Investments	7	25
Recurring | Level 2 | U.S. Treasury and federal agency securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	3,917	3,230
Investments	334	168
Recurring | Level 2 | State and municipal
Assets, Fair Value Disclosure [Abstract]
Trading account assets	1,681	1,995
Investments	1,953	1,849
Recurring | Level 2 | Foreign government
Assets, Fair Value Disclosure [Abstract]
Trading account assets	26,703	31,485
Investments	67,213	61,112
Recurring | Level 2 | Corporate
Assets, Fair Value Disclosure [Abstract]
Trading account assets	14,577	16,156
Investments	3,273	2,871
Recurring | Level 2 | Equity securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	8,946	10,047
Investments	172	177
Recurring | Level 2 | Asset-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	1,404	981
Investments	275	300
Recurring | Level 2 | Other trading assets
Assets, Fair Value Disclosure [Abstract]
Trading account assets	19,577	20,346
Investments	4,936	4,877
Recurring | Level 2 | Non-marketable equity securities
Assets, Fair Value Disclosure [Abstract]
Investments	7	28
Recurring | Level 2 | Trading non-derivative assets
Assets, Fair Value Disclosure [Abstract]
Trading account assets	110,305	120,195
Recurring | Level 2 | Trading account derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	452,167	378,162
Recurring | Level 2 | Trading account derivatives | Interest rate contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	155,912	161,500
Recurring | Level 2 | Trading account derivatives | Foreign exchange contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	185,093	134,912
Recurring | Level 2 | Trading account derivatives | Equity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	53,351	43,904
Recurring | Level 2 | Trading account derivatives | Commodity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	47,253	28,547
Recurring | Level 2 | Trading account derivatives | Credit derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	10,558	9,299
Recurring | Level 2 | Non-trading derivatives and other financial assets measured on a recurring basis
Assets, Fair Value Disclosure [Abstract]
Other assets, gross	6,520	8,194
Recurring | Level 3
Assets, Fair Value Disclosure [Abstract]
Federal funds sold and securities borrowed and purchased under agreements to resell	183	231
Investments	2,263	2,227
Loans held at fair value	325	711
Mortgage servicing rights	600	404
Assets before netting	$ 16,923	$ 14,724
Total as a percentage of gross assets	1.30%	1.10%
Liabilities, Fair Value Disclosure [Abstract]
Interest-bearing deposits	$ 18	$ 183
Federal funds purchased and securities loaned and sold under agreements to repurchase, Gross	593	643
Securities sold, not yet purchased	72	65
Trading liabilities	72	65
Short-term borrowings	81	105
Long-term debt	29,778	25,509
Total liabilities, Gross	$ 39,705	$ 35,176
Total as a percentage of gross liabilities	4.80%	4.70%
Recurring | Level 3 | Trading account liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	$ 9,163	$ 8,670
Recurring | Level 3 | Trading account liabilities | Interest rate contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	2,256	2,172
Recurring | Level 3 | Trading account liabilities | Foreign exchange contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	861	726
Recurring | Level 3 | Trading account liabilities | Equity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	2,286	3,447
Recurring | Level 3 | Trading account liabilities | Commodity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	2,168	1,375
Recurring | Level 3 | Trading account liabilities | Credit derivatives
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	1,592	950
Recurring | Level 3 | Other financial liabilities measured on a recurring basis
Liabilities, Fair Value Disclosure [Abstract]
Other liabilities, gross	0	1
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	999	681
Investments	68	145
Recurring | Level 3 | Mortgage securitizations - U.S. agency-sponsored
Assets, Fair Value Disclosure [Abstract]
Trading account assets	708	496
Investments	28	51
Recurring | Level 3 | Residential
Assets, Fair Value Disclosure [Abstract]
Trading account assets	153	104
Investments	40	94
Recurring | Level 3 | Commercial
Assets, Fair Value Disclosure [Abstract]
Trading account assets	138	81
Investments	0	0
Recurring | Level 3 | U.S. Treasury and federal agency securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	1	4
Investments	0	1
Recurring | Level 3 | State and municipal
Assets, Fair Value Disclosure [Abstract]
Trading account assets	80	37
Investments	539	772
Recurring | Level 3 | Foreign government
Assets, Fair Value Disclosure [Abstract]
Trading account assets	364	23
Investments	1,001	786
Recurring | Level 3 | Corporate
Assets, Fair Value Disclosure [Abstract]
Trading account assets	537	412
Investments	334	188
Recurring | Level 3 | Equity securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	133	174
Investments	10	16
Recurring | Level 3 | Asset-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	554	613
Investments	1	3
Recurring | Level 3 | Other trading assets
Assets, Fair Value Disclosure [Abstract]
Trading account assets	816	576
Investments	0	0
Recurring | Level 3 | Non-marketable equity securities
Assets, Fair Value Disclosure [Abstract]
Investments	310	316
Recurring | Level 3 | Trading non-derivative assets
Assets, Fair Value Disclosure [Abstract]
Trading account assets	3,484	2,520
Recurring | Level 3 | Trading account derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	10,005	8,558
Recurring | Level 3 | Trading account derivatives | Interest rate contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	3,137	3,898
Recurring | Level 3 | Trading account derivatives | Foreign exchange contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	1,017	637
Recurring | Level 3 | Trading account derivatives | Equity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	2,185	1,307
Recurring | Level 3 | Trading account derivatives | Commodity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	2,423	1,797
Recurring | Level 3 | Trading account derivatives | Credit derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	1,243	919
Recurring | Level 3 | Non-trading derivatives and other financial assets measured on a recurring basis
Assets, Fair Value Disclosure [Abstract]
Other assets, gross	$ 63	$ 73