FAIR VALUE MEASUREMENT - Items Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022
Assets, Fair Value Disclosure [Abstract]
Federal funds sold and securities borrowed and purchased under agreements to resell, Netting	$ (320,988)		$ (248,214)
Trading account assets	458,072		411,756
Netting agreements	(316,493)		(308,431)
Netting of cash collateral received	(19,843)		(21,226)
Trading derivatives	50,942		57,717
Investments	490,671		519,085
Held at fair value	8,106		7,594
Liabilities, Fair Value Disclosure [Abstract]
Federal funds purchased and securities loaned and sold under agreements to repurchase, Netting	(320,988)		(248,214)
Netting agreements	(316,493)		(308,431)
Netting of cash collateral paid	(25,082)		(26,101)
Total derivative liabilities	47,589		50,679
Marketable equity securities carried at fair value	207		258
Allowance for credit losses	18,356	$ 18,216	18,145	$ 17,629	$ 17,496	$ 16,974
Non-marketable equity securities | Carried at cost
Assets, Fair Value Disclosure [Abstract]
Investments	5,300		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	25		25
Recurring
Assets, Fair Value Disclosure [Abstract]
Federal funds sold and securities borrowed and purchased under agreements to resell	465,840		453,854
Federal funds sold and securities borrowed and purchased under agreements to resell, Netting	(317,885)		(247,795)
Federal funds sold and securities borrowed and purchased under agreements to resell	147,955		206,059
Investments	235,274		257,677
Held at fair value	8,106		7,594
Mortgage servicing rights	683		691
Assets before netting	1,520,744		1,474,257
Netting, Assets, total of netting agreements and cash collateral received	(654,221)		(577,452)
Total assets	866,523		896,805
Liabilities, Fair Value Disclosure [Abstract]
Interest-bearing deposits	4,112		2,440
Federal funds purchased and securities loaned and sold under agreements to repurchase, Gross	273,124		228,438
Federal funds purchased and securities loaned and sold under agreements to repurchase, Netting	(210,266)		(165,953)
Federal funds purchased and securities loaned and sold under agreements to repurchase	62,858		62,485
Securities sold, not yet purchased	94,930		104,658
Trading liabilities	94,945		104,666
Short-term borrowings	11,896		6,545
Long-term debt	117,286		116,338
Total liabilities, Gross	896,882		848,072
Total liabilities, Netting	(551,841)		(500,485)
Total liabilities	345,041		347,587
Recurring | Trading account liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	389,164		385,211
Total trading derivatives and cash collateral, liability	389,164		385,211
Netting agreements	(316,493)		(308,431)
Netting of cash collateral paid	(25,082)		(26,101)
Netting, Liabilities, total of netting agreements and cash collateral received	(341,575)		(334,532)
Total derivative liabilities	47,589		50,679
Recurring | Trading account liabilities | Interest rate contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	135,005		153,186
Recurring | Trading account liabilities | Foreign exchange contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	155,104		157,201
Recurring | Trading account liabilities | Equity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	74,547		47,946
Recurring | Trading account liabilities | Commodity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	16,294		18,796
Recurring | Trading account liabilities | Credit derivatives
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	8,214		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	6,355		4,434
Total other assets and cash collateral, gross	6,355		4,434
Recurring | Other trading liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	15		8
Recurring | Mortgage-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	79,691		81,756
Investments	32,503		30,139
Recurring | Mortgage securitizations - U.S. agency-sponsored
Assets, Fair Value Disclosure [Abstract]
Trading account assets	78,372		80,376
Investments	31,877		29,715
Recurring | Residential
Assets, Fair Value Disclosure [Abstract]
Trading account assets	548		714
Investments	625		423
Recurring | Commercial Mortgage-Backed Securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	771		666
Investments	1		1
Recurring | U.S. Treasury and federal agency securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	133,067		115,256
Investments	59,544		80,361
Recurring | State and municipal
Assets, Fair Value Disclosure [Abstract]
Trading account assets	199		597
Investments	1,887		2,131
Recurring | Foreign government
Assets, Fair Value Disclosure [Abstract]
Trading account assets	94,341		72,495
Investments	129,640		131,198
Recurring | Corporate
Assets, Fair Value Disclosure [Abstract]
Trading account assets	20,973		19,074
Investments	5,682		5,412
Recurring | Equity securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	56,451		45,393
Investments	207		258
Recurring | Asset-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	1,737		1,754
Investments	838		938
Recurring | Other debt securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	20,671		17,714
Investments	4,350		6,757
Recurring | Non-marketable equity securities
Assets, Fair Value Disclosure [Abstract]
Investments	623		483
Recurring | Trading non-derivative assets
Assets, Fair Value Disclosure [Abstract]
Trading account assets	407,130		354,039
Recurring | Trading account derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	387,278		387,374
Trading derivative, asset, gross net cash collateral paid	387,278		387,374
Netting agreements	(316,493)		(308,431)
Netting of cash collateral received	(19,843)		(21,226)
Total trading derivatives, netting	(336,336)		(329,657)
Trading derivatives	50,942		57,717
Recurring | Trading account derivatives | Interest rate contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	143,670		158,494
Recurring | Trading account derivatives | Foreign exchange contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	158,996		159,694
Recurring | Trading account derivatives | Equity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	62,736		43,278
Recurring | Trading account derivatives | Commodity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	13,854		17,569
Recurring | Trading account derivatives | Credit derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	8,022		8,339
Recurring | Other financial assets
Assets, Fair Value Disclosure [Abstract]
Total trading derivatives, netting	0		0
Total other assets and cash collateral, gross	16,433		13,028
Other assets	16,433		13,028
Recurring | Level 1
Assets, Fair Value Disclosure [Abstract]
Federal funds sold and securities borrowed and purchased under agreements to resell	0		0
Investments	123,964		143,034
Held at fair value	0		0
Mortgage servicing rights	0		0
Assets before netting	$ 375,764		$ 339,746
Total as a percentage of gross assets	24.70%		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	79,939		91,163
Trading liabilities	79,939		91,163
Short-term borrowings	0		0
Long-term debt	0		0
Total liabilities, Gross	$ 85,661		$ 95,528
Total as a percentage of gross liabilities	9.60%		11.30%
Recurring | Level 1 | Trading account liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	$ 160		$ 67
Recurring | Level 1 | Trading account liabilities | Interest rate contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	22		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	138		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	5,562		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	131,604		112,851
Investments	59,544		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	62,485		44,203
Investments	60,706		60,133
Recurring | Level 1 | Corporate
Assets, Fair Value Disclosure [Abstract]
Trading account assets	1,851		1,858
Investments	3,519		2,680
Recurring | Level 1 | Equity securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	49,421		32,966
Investments	195		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	0		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	245,361		191,976
Recurring | Level 1 | Trading account derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	117		59
Recurring | Level 1 | Trading account derivatives | Interest rate contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	31		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	84		8
Recurring | Level 1 | Trading account derivatives | Commodity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	2		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	6,322		4,677
Recurring | Level 2
Assets, Fair Value Disclosure [Abstract]
Federal funds sold and securities borrowed and purchased under agreements to resell	465,704		453,715
Investments	110,020		112,844
Held at fair value	7,759		7,167
Mortgage servicing rights	0		0
Assets before netting	$ 1,135,301		$ 1,121,860
Total as a percentage of gross assets	74.70%		76.10%
Liabilities, Fair Value Disclosure [Abstract]
Interest-bearing deposits	$ 4,070		$ 2,411
Federal funds purchased and securities loaned and sold under agreements to repurchase, Gross	272,832		228,048
Securities sold, not yet purchased	14,955		13,460
Trading liabilities	14,970		13,468
Short-term borrowings	11,675		6,064
Long-term debt	94,977		77,958
Total liabilities, Gross	$ 781,171		$ 704,559
Total as a percentage of gross liabilities	87.10%		83.00%
Recurring | Level 2 | Trading account liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	$ 381,855		$ 376,480
Recurring | Level 2 | Trading account liabilities | Interest rate contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	132,924		149,914
Recurring | Level 2 | Trading account liabilities | Foreign exchange contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	154,525		156,474
Recurring | Level 2 | Trading account liabilities | Equity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	71,232		44,894
Recurring | Level 2 | Trading account liabilities | Commodity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	15,679		17,964
Recurring | Level 2 | Trading account liabilities | Credit derivatives
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	7,495		7,234
Recurring | Level 2 | Other financial liabilities
Liabilities, Fair Value Disclosure [Abstract]
Other liabilities, gross	792		130
Recurring | Level 2 | Other trading liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	15		8
Recurring | Level 2 | Mortgage-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	78,803		80,856
Investments	32,444		29,948
Recurring | Level 2 | Mortgage securitizations - U.S. agency-sponsored
Assets, Fair Value Disclosure [Abstract]
Trading account assets	77,641		79,795
Investments	31,845		29,640
Recurring | Level 2 | Residential
Assets, Fair Value Disclosure [Abstract]
Trading account assets	477		597
Investments	598		307
Recurring | Level 2 | Commercial Mortgage-Backed Securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	685		464
Investments	1		1
Recurring | Level 2 | U.S. Treasury and federal agency securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	1,463		2,398
Investments	0		299
Recurring | Level 2 | State and municipal
Assets, Fair Value Disclosure [Abstract]
Trading account assets	178		594
Investments	1,451		1,589
Recurring | Level 2 | Foreign government
Assets, Fair Value Disclosure [Abstract]
Trading account assets	31,825		28,238
Investments	68,922		70,871
Recurring | Level 2 | Corporate
Assets, Fair Value Disclosure [Abstract]
Trading account assets	18,862		16,716
Investments	2,013		2,370
Recurring | Level 2 | Equity securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	6,744		12,135
Investments	2		72
Recurring | Level 2 | Asset-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	1,522		1,223
Investments	838		938
Recurring | Level 2 | Other debt securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	20,121		16,784
Investments	4,350		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	159,518		158,944
Recurring | Level 2 | Trading account derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	382,214		380,869
Recurring | Level 2 | Trading account derivatives | Interest rate contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	141,896		156,307
Recurring | Level 2 | Trading account derivatives | Foreign exchange contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	158,414		158,672
Recurring | Level 2 | Trading account derivatives | Equity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	61,711		41,870
Recurring | Level 2 | Trading account derivatives | Commodity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	12,836		16,456
Recurring | Level 2 | Trading account derivatives | Credit derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	7,357		7,564
Recurring | Level 2 | Other financial assets
Assets, Fair Value Disclosure [Abstract]
Other assets, gross	10,086		8,321
Recurring | Level 3
Assets, Fair Value Disclosure [Abstract]
Federal funds sold and securities borrowed and purchased under agreements to resell	136		139
Investments	1,290		1,799
Held at fair value	347		427
Mortgage servicing rights	683		691
Assets before netting	$ 9,679		$ 12,651
Total as a percentage of gross assets	0.60%		0.90%
Liabilities, Fair Value Disclosure [Abstract]
Interest-bearing deposits	$ 42		$ 29
Federal funds purchased and securities loaned and sold under agreements to repurchase, Gross	292		390
Securities sold, not yet purchased	36		35
Trading liabilities	36		35
Short-term borrowings	221		481
Long-term debt	22,309		38,380
Total liabilities, Gross	$ 30,050		$ 47,985
Total as a percentage of gross liabilities	3.30%		5.70%
Recurring | Level 3 | Trading account liabilities
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	$ 7,149		$ 8,664
Recurring | Level 3 | Trading account liabilities | Interest rate contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	2,059		3,223
Recurring | Level 3 | Trading account liabilities | Foreign exchange contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	579		727
Recurring | Level 3 | Trading account liabilities | Equity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	3,177		3,034
Recurring | Level 3 | Trading account liabilities | Commodity contracts
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	615		832
Recurring | Level 3 | Trading account liabilities | Credit derivatives
Liabilities, Fair Value Disclosure [Abstract]
Trading derivatives, liability	719		848
Recurring | Level 3 | Other financial liabilities
Liabilities, Fair Value Disclosure [Abstract]
Other liabilities, gross	1		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	888		899
Investments	59		191
Recurring | Level 3 | Mortgage securitizations - U.S. agency-sponsored
Assets, Fair Value Disclosure [Abstract]
Trading account assets	731		581
Investments	32		75
Recurring | Level 3 | Residential
Assets, Fair Value Disclosure [Abstract]
Trading account assets	71		116
Investments	27		116
Recurring | Level 3 | Commercial Mortgage-Backed Securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	86		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	21		3
Investments	436		542
Recurring | Level 3 | Foreign government
Assets, Fair Value Disclosure [Abstract]
Trading account assets	31		54
Investments	12		194
Recurring | Level 3 | Corporate
Assets, Fair Value Disclosure [Abstract]
Trading account assets	260		500
Investments	150		362
Recurring | Level 3 | Equity securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	286		292
Investments	10		27
Recurring | Level 3 | Asset-backed securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	215		531
Investments	0		0
Recurring | Level 3 | Other debt securities
Assets, Fair Value Disclosure [Abstract]
Trading account assets	550		833
Investments	0		0
Recurring | Level 3 | Non-marketable equity securities
Assets, Fair Value Disclosure [Abstract]
Investments	623		483
Recurring | Level 3 | Trading non-derivative assets
Assets, Fair Value Disclosure [Abstract]
Trading account assets	2,251		3,119
Recurring | Level 3 | Trading account derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	4,947		6,446
Recurring | Level 3 | Trading account derivatives | Interest rate contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	1,743		2,138
Recurring | Level 3 | Trading account derivatives | Foreign exchange contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	582		1,022
Recurring | Level 3 | Trading account derivatives | Equity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	941		1,400
Recurring | Level 3 | Trading account derivatives | Commodity contracts
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	1,016		1,111
Recurring | Level 3 | Trading account derivatives | Credit derivatives
Assets, Fair Value Disclosure [Abstract]
Trading derivatives, asset, Gross	665		775
Recurring | Level 3 | Other financial assets
Assets, Fair Value Disclosure [Abstract]
Other assets, gross	$ 25		$ 30