LOANS - Consumer Loans, Delinquencies and Non-Accrual Details (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
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	$ 688,922		$ 688,922		$ 689,362
Held at fair value	8,106		8,106		7,594
Reversal of accrued interest	400	$ 300	1,200	$ 800
Consumer loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	389,151		389,151		389,197
Non-accrual loans for which there is no ACLL	141		141		159
Non-accrual loans for which there is an ACLL	1,081		1,081		1,156
Total non-accrual	1,222		1,222		1,315
90 days  past due and accruing	2,702		2,702		2,674
Total excluding portfolio layer cumulative basis adjustments	388,481		388,481
Held at fair value	302		302		313
Unearned income	883		883		802
Accrued interest receivable	1,000		1,000		1,000
Consumer loans | Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income					382,466
Total excluding portfolio layer cumulative basis adjustments	381,781		381,781
Consumer loans | 30–89 days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income					3,259
Total excluding portfolio layer cumulative basis adjustments	3,213		3,213
Consumer loans | 90+ days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income					3,233
Total excluding portfolio layer cumulative basis adjustments	3,255		3,255
Consumer loans | Past Due | Government-guaranteed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income					239
Total excluding portfolio layer cumulative basis adjustments	232		232
Consumer loans | In North America offices
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	314,375		314,375		313,158
Non-accrual loans for which there is no ACLL	141		141		159
Non-accrual loans for which there is an ACLL	574		574		569
Total non-accrual	715		715		728
90 days  past due and accruing	2,633		2,633		2,586
Consumer loans | In North America offices | Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	308,313		308,313		307,127
Consumer loans | In North America offices | 30–89 days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	2,876		2,876		2,895
Consumer loans | In North America offices | 90+ days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	2,954		2,954		2,897
Consumer loans | In North America offices | 90+ days past due | Banking
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	26,000		26,000		29,200
Consumer loans | In North America offices | Past Due | Government-guaranteed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	232		232		239
Consumer loans | In offices outside North America
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	74,106		74,106		76,039
Non-accrual loans for which there is no ACLL	0		0		0
Non-accrual loans for which there is an ACLL	507		507		587
Total non-accrual	507		507		587
90 days  past due and accruing	69		69		88
Consumer loans | In offices outside North America | Classifiably managed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	18,156		18,156		17,007
Consumer loans | In offices outside North America | Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	73,468		73,468		75,339
Consumer loans | In offices outside North America | 30–89 days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	337		337		364
Consumer loans | In offices outside North America | 90+ days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	301		301		336
Consumer loans | In offices outside North America | 90+ days past due | Banking
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	18,200		18,200		17,000
Consumer loans | In offices outside North America | Past Due | Government-guaranteed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	0		0		0
Consumer loans | Residential mortgages
Financing Receivable, Past Due [Line Items]
Held at fair value	302		302		313
Consumer loans | Residential mortgages | In North America offices
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	114,126		114,126		108,711
Non-accrual loans for which there is no ACLL	110		110		105
Non-accrual loans for which there is an ACLL	389		389		384
Total non-accrual	499		499		489
90 days  past due and accruing	120		120		120
Mortgage loans in process of foreclosure	100		100		100
Consumer loans | Residential mortgages | In North America offices | Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	113,186		113,186		107,720
Consumer loans | Residential mortgages | In North America offices | 30–89 days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	395		395		462
Consumer loans | Residential mortgages | In North America offices | 30–89 days past due | Government-guaranteed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	100		100
Consumer loans | Residential mortgages | In North America offices | 90+ days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	314		314		294
Consumer loans | Residential mortgages | In North America offices | 90+ days past due | Government-guaranteed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income					100
Consumer loans | Residential mortgages | In North America offices | Past Due | Government-guaranteed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	231		231		235
Consumer loans | Residential mortgages | In offices outside North America
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	25,702		25,702		26,426
Non-accrual loans for which there is no ACLL	0		0		0
Non-accrual loans for which there is an ACLL	197		197		243
Total non-accrual	197		197		243
90 days  past due and accruing	0		0		0
Mortgage loans in process of foreclosure	100		100		100
Consumer loans | Residential mortgages | In offices outside North America | Classifiably managed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	0		0		0
Consumer loans | Residential mortgages | In offices outside North America | Global Wealth Management Business
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	20,000		20,000		19,900
Consumer loans | Residential mortgages | In offices outside North America | Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	25,603		25,603		26,309
Consumer loans | Residential mortgages | In offices outside North America | 30–89 days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	40		40		48
Consumer loans | Residential mortgages | In offices outside North America | 90+ days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	59		59		69
Consumer loans | Residential mortgages | In offices outside North America | Past Due | Government-guaranteed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	0		0		0
Consumer loans | Home equity loans | In North America offices
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	3,242		3,242		3,592
Non-accrual loans for which there is no ACLL	25		25		48
Non-accrual loans for which there is an ACLL	133		133		126
Total non-accrual	158		158		174
90 days  past due and accruing	0		0		0
Home equity loans in process of foreclosure	100		100		100
Consumer loans | Home equity loans | In North America offices | Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	3,137		3,137		3,471
Consumer loans | Home equity loans | In North America offices | 30–89 days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	28		28		36
Consumer loans | Home equity loans | In North America offices | 90+ days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	77		77		85
Consumer loans | Home equity loans | In North America offices | Past Due | Government-guaranteed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	0		0		0
Consumer loans | Credit cards | In North America offices
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	163,699		163,699		164,720
Non-accrual loans for which there is no ACLL	0		0		0
Non-accrual loans for which there is an ACLL	0		0		0
Total non-accrual	0		0		0
90 days  past due and accruing	2,510		2,510		2,461
Consumer loans | Credit cards | In North America offices | Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	158,833		158,833		159,966
Consumer loans | Credit cards | In North America offices | 30–89 days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	2,356		2,356		2,293
Consumer loans | Credit cards | In North America offices | 90+ days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	2,510		2,510		2,461
Consumer loans | Credit cards | In North America offices | Past Due | Government-guaranteed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	0		0		0
Consumer loans | Credit cards | In offices outside North America
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	12,930		12,930		14,233
Non-accrual loans for which there is no ACLL	0		0		0
Non-accrual loans for which there is an ACLL	204		204		211
Total non-accrual	204		204		211
90 days  past due and accruing	69		69		88
Consumer loans | Credit cards | In offices outside North America | Classifiably managed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	0		0		0
Consumer loans | Credit cards | In offices outside North America | Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	12,532		12,532		13,797
Consumer loans | Credit cards | In offices outside North America | 30–89 days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	194		194		209
Consumer loans | Credit cards | In offices outside North America | 90+ days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	204		204		227
Consumer loans | Credit cards | In offices outside North America | Past Due | Government-guaranteed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	0		0		0
Consumer loans | Personal, small business and other | In North America offices
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	33,308		33,308		36,135
Non-accrual loans for which there is no ACLL	6		6		6
Non-accrual loans for which there is an ACLL	52		52		59
Total non-accrual	58		58		65
90 days  past due and accruing	3		3		5
Consumer loans | Personal, small business and other | In North America offices | Global Wealth Management Business
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	$ 28,300		$ 28,300		$ 31,600
Consumer loans | Personal, small business and other | In North America offices | Global Wealth Management Business | Internal Investment Grade
Financing Receivable, Past Due [Line Items]
Percentage of loans rated investment grade	82.00%		82.00%		92.00%
Consumer loans | Personal, small business and other | In North America offices | Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	$ 33,157		$ 33,157		$ 35,970
Consumer loans | Personal, small business and other | In North America offices | 30–89 days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	97		97		104
Consumer loans | Personal, small business and other | In North America offices | 90+ days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	53		53		57
Consumer loans | Personal, small business and other | In North America offices | Past Due | Government-guaranteed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	1		1		4
Consumer loans | Personal, small business and other | In offices outside North America
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	35,474		35,474		35,380
Non-accrual loans for which there is no ACLL	0		0		0
Non-accrual loans for which there is an ACLL	106		106		133
Total non-accrual	106		106		133
90 days  past due and accruing	0		0		0
Consumer loans | Personal, small business and other | In offices outside North America | Classifiably managed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	18,156		18,156		$ 17,007
Consumer loans | Personal, small business and other | In offices outside North America | Internal Investment Grade
Financing Receivable, Past Due [Line Items]
Percentage of loans rated investment grade					92.00%
Consumer loans | Personal, small business and other | In offices outside North America | Global Wealth Management Business
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	$ 26,300		$ 26,300		$ 24,900
Consumer loans | Personal, small business and other | In offices outside North America | Global Wealth Management Business | Classifiably managed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income					$ 17,000
Consumer loans | Personal, small business and other | In offices outside North America | Global Wealth Management Business | Internal Investment Grade
Financing Receivable, Past Due [Line Items]
Percentage of loans rated investment grade	58.00%		58.00%		74.00%
Consumer loans | Personal, small business and other | In offices outside North America | Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	$ 35,333		$ 35,333		$ 35,233
Consumer loans | Personal, small business and other | In offices outside North America | 30–89 days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	103		103		107
Consumer loans | Personal, small business and other | In offices outside North America | 90+ days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	38		38		40
Consumer loans | Personal, small business and other | In offices outside North America | Past Due | Government-guaranteed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	$ 0		$ 0		$ 0