LOANS - Consumer Loans, Delinquencies and Non-Accrual Details (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	$ 666,348		$ 666,348		$ 657,221
Held at fair value	7,411		7,411		5,360
Reversal of accrued interest	300	$ 200	800	$ 500
Consumer loans
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	377,714		377,714		368,067
Non-accrual loans for which there is no ACLL	152		152		140
Non-accrual loans for which there is an ACLL	1,150		1,150		1,177
Total non-accrual	1,302		1,302		1,317
90 days  past due and accruing	2,249		2,249		1,658
Held at fair value	222		222		237
Unearned income	789		789		712
Accrued interest receivable	1,000		1,000		1,000
Consumer loans | Classifiably managed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	29,828		29,828		31,478
Consumer loans | Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	371,736		371,736		363,256
Consumer loans | 30–89 days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	2,951		2,951		2,372
Consumer loans | 90+ days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	2,792		2,792		2,153
Consumer loans | Past Due | Government-guaranteed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	235		235		286
Consumer loans | In North America offices
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	302,453		302,453		289,014
Non-accrual loans for which there is no ACLL	152		152		140
Non-accrual loans for which there is an ACLL	572		572		608
Total non-accrual	724		724		748
90 days  past due and accruing	2,170		2,170		1,589
Consumer loans | In North America offices | Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	297,135		297,135		284,782
Consumer loans | In North America offices | 30–89 days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	2,606		2,606		2,058
Consumer loans | In North America offices | 90+ days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	2,477		2,477		1,888
Consumer loans | In North America offices | 90+ days past due | Personal Banking and Wealth Management
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	29,800		29,800		31,500
Consumer loans | In North America offices | Past Due | Government-guaranteed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	235		235		286
Consumer loans | In offices outside North America
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	75,261		75,261		79,053
Non-accrual loans for which there is no ACLL	0		0		0
Non-accrual loans for which there is an ACLL	578		578		569
Total non-accrual	578		578		569
90 days  past due and accruing	79		79		69
Consumer loans | In offices outside North America | Classifiably managed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	16,954		16,954		17,762
Consumer loans | In offices outside North America | Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	74,601		74,601		78,474
Consumer loans | In offices outside North America | 30–89 days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	345		345		314
Consumer loans | In offices outside North America | 90+ days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	315		315		265
Consumer loans | In offices outside North America | 90+ days past due | Personal Banking and Wealth Management
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	17,000		17,000		17,800
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]
Loans, net of unearned income	106,369		106,369		96,039
Held at fair value	222		222		237
Consumer loans | Residential mortgages | Classifiably managed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	0		0
Consumer loans | Residential mortgages | In North America offices
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	106,369		106,369		96,039
Non-accrual loans for which there is no ACLL	102		102		86
Non-accrual loans for which there is an ACLL	384		384		434
Total non-accrual	486		486		520
90 days  past due and accruing	120		120		163
Mortgage loans in process of foreclosure	200		200		100
Consumer loans | Residential mortgages | In North America offices | Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	105,453		105,453		95,023
Consumer loans | Residential mortgages | In North America offices | 30–89 days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	389		389		421
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		100
Consumer loans | Residential mortgages | In North America offices | 90+ days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	294		294		316
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		100		200
Consumer loans | Residential mortgages | In North America offices | Past Due | Government-guaranteed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	233		233		279
Consumer loans | Residential mortgages | In offices outside North America
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	26,389		26,389		28,114
Non-accrual loans for which there is no ACLL	0		0		0
Non-accrual loans for which there is an ACLL	258		258		305
Total non-accrual	258		258		305
90 days  past due and accruing	20		20		13
Mortgage loans in process of foreclosure	0		0		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	20,000		20,000		19,800
Consumer loans | Residential mortgages | In offices outside North America | Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	26,268		26,268		27,946
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	49		49		62
Consumer loans | Residential mortgages | In offices outside North America | 90+ days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	72		72		106
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
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	3,796		3,796		4,580
Consumer loans | Home equity loans | Classifiably managed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	0		0
Consumer loans | Home equity loans | In North America offices
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	3,796		3,796		4,580
Non-accrual loans for which there is no ACLL	47		47		51
Non-accrual loans for which there is an ACLL	132		132		151
Total non-accrual	179		179		202
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	3,675		3,675		4,407
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	32		32		38
Consumer loans | Home equity loans | In North America offices | 90+ days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	89		89		135
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
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	155,092		155,092		150,098
Consumer loans | Credit cards | Classifiably managed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	0		0
Consumer loans | Credit cards | In North America offices
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	155,698		155,698		150,643
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	2,045		2,045		1,415
Consumer loans | Credit cards | In North America offices | Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	151,560		151,560		147,717
Consumer loans | Credit cards | In North America offices | 30–89 days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	2,093		2,093		1,511
Consumer loans | Credit cards | In North America offices | 90+ days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	2,045		2,045		1,415
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	13,573		13,573		12,955
Non-accrual loans for which there is no ACLL	0		0		0
Non-accrual loans for which there is an ACLL	187		187		127
Total non-accrual	187		187		127
90 days  past due and accruing	59		59		56
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	13,179		13,179		12,659
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	192		192		147
Consumer loans | Credit cards | In offices outside North America | 90+ days past due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	202		202		149
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
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	35,691		35,691		36,812
Consumer loans | Personal, small business and other | Classifiably managed
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	29,828		29,828		31,478
Consumer loans | Personal, small business and other | In North America offices
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	36,590		36,590		37,752
Non-accrual loans for which there is no ACLL	3		3		3
Non-accrual loans for which there is an ACLL	56		56		23
Total non-accrual	59		59		26
90 days  past due and accruing	5		5		11
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	$ 32,300		$ 32,300		$ 34,000
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	96.00%		96.00%		98.00%
Consumer loans | Personal, small business and other | In North America offices | Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	$ 36,447		$ 36,447		$ 37,635
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	92		92		88
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	49		49		22
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	2		2		7
Consumer loans | Personal, small business and other | In offices outside North America
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	35,299		35,299		37,984
Non-accrual loans for which there is no ACLL	0		0		0
Non-accrual loans for which there is an ACLL	133		133		137
Total non-accrual	133		133		137
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	16,954		16,954		$ 17,762
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					98.00%
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	$ 24,900		$ 24,900		$ 26,600
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					$ 17,800
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	93.00%		93.00%		94.00%
Consumer loans | Personal, small business and other | In offices outside North America | Current
Financing Receivable, Past Due [Line Items]
Loans, net of unearned income	$ 35,154		$ 35,154		$ 37,869
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	104		104		105
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	41		41		10
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