COMMISSIONS AND FEES; ADMINISTRATION AND OTHER FIDUCIARY FEES - Commissions and Fees Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Commissions and fees
Total commissions and fees	$ 3,670	$ 3,021
Investment banking
Commissions and fees
Total commissions and fees	1,624	1,040
Brokerage commissions
Commissions and fees
Total commissions and fees	942	826
Interchange fees
Commissions and fees
Total commissions and fees	2,064	2,178
Card-related loan fees
Commissions and fees
Total commissions and fees	182	177
Card rewards and partner payments
Commissions and fees
Total commissions and fees	(2,171)	(2,242)
Deposit-related fees
Commissions and fees
Total commissions and fees	329	348
Transactional service fees
Commissions and fees
Total commissions and fees	265	251
Corporate finance
Commissions and fees
Total commissions and fees	158	146
Insurance distribution revenue
Commissions and fees
Total commissions and fees	135	129
Insurance premiums
Commissions and fees
Total commissions and fees	20	43
Loan servicing
Commissions and fees
Total commissions and fees	23	39
Other
Commissions and fees
Total commissions and fees	99	86
Overdraft fees
Commissions and fees
Total commissions and fees	24	31
Commissions and fees
Commissions and fees
Revenue not accounted for under ASC 606, revenue from contracts with customers	(1,749)	(1,802)
ICG
Commissions and fees
Total commissions and fees	3,028	2,400
ICG | Investment banking
Commissions and fees
Total commissions and fees	1,624	1,040
ICG | Brokerage commissions
Commissions and fees
Total commissions and fees	615	577
ICG | Interchange fees
Commissions and fees
Total commissions and fees	158	261
ICG | Card-related loan fees
Commissions and fees
Total commissions and fees	5	11
ICG | Card rewards and partner payments
Commissions and fees
Total commissions and fees	(75)	(149)
ICG | Deposit-related fees
Commissions and fees
Total commissions and fees	244	233
ICG | Transactional service fees
Commissions and fees
Total commissions and fees	241	227
ICG | Corporate finance
Commissions and fees
Total commissions and fees	158	146
ICG | Insurance distribution revenue
Commissions and fees
Total commissions and fees	5	4
ICG | Insurance premiums
Commissions and fees
Total commissions and fees	0	0
ICG | Loan servicing
Commissions and fees
Total commissions and fees	12	20
ICG | Other
Commissions and fees
Total commissions and fees	41	30
GCB
Commissions and fees
Total commissions and fees	638	613
GCB | Investment banking
Commissions and fees
Total commissions and fees	0	0
GCB | Brokerage commissions
Commissions and fees
Total commissions and fees	327	249
GCB | Interchange fees
Commissions and fees
Total commissions and fees	1,906	1,917
GCB | Card-related loan fees
Commissions and fees
Total commissions and fees	177	166
GCB | Card rewards and partner payments
Commissions and fees
Total commissions and fees	(2,096)	(2,093)
GCB | Deposit-related fees
Commissions and fees
Total commissions and fees	85	115
GCB | Transactional service fees
Commissions and fees
Total commissions and fees	24	24
GCB | Corporate finance
Commissions and fees
Total commissions and fees	0	0
GCB | Insurance distribution revenue
Commissions and fees
Total commissions and fees	130	125
GCB | Insurance premiums
Commissions and fees
Total commissions and fees	20	43
GCB | Loan servicing
Commissions and fees
Total commissions and fees	7	11
GCB | Other
Commissions and fees
Total commissions and fees	58	56
Corporate/Other
Commissions and fees
Total commissions and fees	4	8
Corporate/Other | Investment banking
Commissions and fees
Total commissions and fees	0	0
Corporate/Other | Brokerage commissions
Commissions and fees
Total commissions and fees	0	0
Corporate/Other | Interchange fees
Commissions and fees
Total commissions and fees	0	0
Corporate/Other | Card-related loan fees
Commissions and fees
Total commissions and fees	0	0
Corporate/Other | Card rewards and partner payments
Commissions and fees
Total commissions and fees	0	0
Corporate/Other | Deposit-related fees
Commissions and fees
Total commissions and fees	0	0
Corporate/Other | Transactional service fees
Commissions and fees
Total commissions and fees	0	0
Corporate/Other | Corporate finance
Commissions and fees
Total commissions and fees	0	0
Corporate/Other | Insurance distribution revenue
Commissions and fees
Total commissions and fees	0	0
Corporate/Other | Insurance premiums
Commissions and fees
Total commissions and fees	0	0
Corporate/Other | Loan servicing
Commissions and fees
Total commissions and fees	4	8
Corporate/Other | Other
Commissions and fees
Total commissions and fees	$ 0	$ 0