LOANS - Consumer Loans, Delinquencies and Non-Accrual Details (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	$ 687,722		$ 687,722		$ 689,362
Unallocated portfolio layer cumulative basis adjustments	(213)		(213)		93
Held at fair value	8,526		8,526		7,594
Reversal of accrued interest	400	$ 300	800	$ 500
Consumer loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	386,117		386,117		389,197
Non-accrual loans for which there is no ACLL	143		143		159
Non-accrual loans for which there is an ACLL	1,109		1,109		1,156
Total non-accrual	1,252		1,252		1,315
90 days  past due and accruing	2,638		2,638		2,674
Total excluding portfolio layer cumulative basis adjustments	386,155		386,155
Unallocated portfolio layer cumulative basis adjustments	(38)		(38)
Held at fair value	294		294		313
Unearned income	852		852		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	379,741		379,741
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	2,971		2,971
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	3,198		3,198
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	245		245
Consumer loans | In North America offices
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	312,833		312,833		313,158
Non-accrual loans for which there is no ACLL	143		143		159
Non-accrual loans for which there is an ACLL	576		576		569
Total non-accrual	719		719		728
90 days  past due and accruing	2,570		2,570		2,586
Consumer loans | In North America offices | Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	307,048		307,048		307,127
Consumer loans | In North America offices | 30–89 days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	2,648		2,648		2,895
Consumer loans | In North America offices | 90+ days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	2,892		2,892		2,897
Consumer loans | In North America offices | 90+ days past due | Personal Banking and Wealth Management [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	26,200		26,200		29,200
Consumer loans | In North America offices | Past Due | Government-guaranteed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	245		245		239
Consumer loans | In offices outside North America
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	73,322		73,322		76,039
Non-accrual loans for which there is no ACLL	0		0		0
Non-accrual loans for which there is an ACLL	533		533		587
Total non-accrual	533		533		587
90 days  past due and accruing	68		68		88
Consumer loans | In offices outside North America | Classifiably managed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	17,472		17,472		17,007
Consumer loans | In offices outside North America | Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	72,693		72,693		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	323		323		364
Consumer loans | In offices outside North America | 90+ days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	306		306		336
Consumer loans | In offices outside North America | 90+ days past due | Personal Banking and Wealth Management [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	17,500		17,500		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	294		294		313
Consumer loans | Residential mortgages | In North America offices
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	112,710		112,710		108,711
Non-accrual loans for which there is no ACLL	115		115		105
Non-accrual loans for which there is an ACLL	393		393		384
Total non-accrual	508		508		489
90 days  past due and accruing	117		117		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	111,763		111,763		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	386		386		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	321		321		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	240		240		235
Consumer loans | Residential mortgages | In offices outside North America
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	25,489		25,489		26,426
Non-accrual loans for which there is no ACLL	0		0		0
Non-accrual loans for which there is an ACLL	235		235		243
Total non-accrual	235		235		243
90 days  past due and accruing	0		0		0
Mortgage loans in process of foreclosure	100		100		0
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	19,600		19,600		19,900
Consumer loans | Residential mortgages | In offices outside North America | Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	25,384		25,384		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	65		65		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	3,338		3,338		3,592
Non-accrual loans for which there is no ACLL	22		22		48
Non-accrual loans for which there is an ACLL	143		143		126
Total non-accrual	165		165		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	3,228		3,228		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	82		82		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	163,467		163,467		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	2,445		2,445		2,461
Consumer loans | Credit cards | In North America offices | Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	158,903		158,903		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	2,119		2,119		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	2,445		2,445		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	13,197		13,197		14,233
Non-accrual loans for which there is no ACLL	0		0		0
Non-accrual loans for which there is an ACLL	198		198		211
Total non-accrual	198		198		211
90 days  past due and accruing	68		68		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	12,805		12,805		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	187		187		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	205		205		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	33,318		33,318		36,135
Non-accrual loans for which there is no ACLL	6		6		6
Non-accrual loans for which there is an ACLL	40		40		59
Total non-accrual	46		46		65
90 days  past due and accruing	8		8		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	$ 28,500		$ 28,500		$ 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	84.00%		84.00%		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	$ 33,154		$ 33,154		$ 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	115		115		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	44		44		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	5		5		4
Consumer loans | Personal, small business and other | In offices outside North America
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	34,636		34,636		35,380
Non-accrual loans for which there is no ACLL	0		0		0
Non-accrual loans for which there is an ACLL	100		100		133
Total non-accrual	100		100		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	17,472		17,472		$ 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	$ 25,000		$ 25,000		$ 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	61.00%		61.00%		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	$ 34,504		$ 34,504		$ 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	96		96		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	36		36		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