COMMISSIONS AND FEES; ADMINISTRATION AND OTHER FIDUCIARY FEES - Commissions and Fees Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Commissions and fees
Total commissions and fees	$ 3,021	$ 2,926
Investment banking
Commissions and fees
Total commissions and fees	1,040	914
Brokerage commissions
Commissions and fees
Total commissions and fees	826	657
Interchange fees
Commissions and fees
Total commissions and fees	2,178	2,262
Card-related loan fees
Commissions and fees
Total commissions and fees	177	173
Card rewards and partner payments
Commissions and fees
Total commissions and fees	(2,242)	(2,214)
Deposit-related fees
Commissions and fees
Total commissions and fees	348	384
Transactional service fees
Commissions and fees
Total commissions and fees	251	231
Corporate finance
Commissions and fees
Total commissions and fees	146	179
Insurance distribution revenue
Commissions and fees
Total commissions and fees	129	136
Insurance premiums
Commissions and fees
Total commissions and fees	43	47
Loan servicing
Commissions and fees
Total commissions and fees	39	78
Other
Commissions and fees
Total commissions and fees	86	79
Overdraft fees
Commissions and fees
Total commissions and fees	31	31
Commissions and fees
Commissions and fees
Revenue not accounted for under ASC 606, revenue from contracts with customers	(1,802)	(1,703)
ICG
Commissions and fees
Total commissions and fees	2,400	2,236
ICG | Investment banking
Commissions and fees
Total commissions and fees	1,040	914
ICG | Brokerage commissions
Commissions and fees
Total commissions and fees	577	471
ICG | Interchange fees
Commissions and fees
Total commissions and fees	261	279
ICG | Card-related loan fees
Commissions and fees
Total commissions and fees	11	13
ICG | Card rewards and partner payments
Commissions and fees
Total commissions and fees	(149)	(153)
ICG | Deposit-related fees
Commissions and fees
Total commissions and fees	233	262
ICG | Transactional service fees
Commissions and fees
Total commissions and fees	227	201
ICG | Corporate finance
Commissions and fees
Total commissions and fees	146	179
ICG | Insurance distribution revenue
Commissions and fees
Total commissions and fees	4	4
ICG | Insurance premiums
Commissions and fees
Total commissions and fees	0	0
ICG | Loan servicing
Commissions and fees
Total commissions and fees	20	50
ICG | Other
Commissions and fees
Total commissions and fees	30	17
GCB
Commissions and fees
Total commissions and fees	613	683
GCB | Investment banking
Commissions and fees
Total commissions and fees	0	0
GCB | Brokerage commissions
Commissions and fees
Total commissions and fees	249	186
GCB | Interchange fees
Commissions and fees
Total commissions and fees	1,917	1,983
GCB | Card-related loan fees
Commissions and fees
Total commissions and fees	166	160
GCB | Card rewards and partner payments
Commissions and fees
Total commissions and fees	(2,093)	(2,061)
GCB | Deposit-related fees
Commissions and fees
Total commissions and fees	115	122
GCB | Transactional service fees
Commissions and fees
Total commissions and fees	24	30
GCB | Corporate finance
Commissions and fees
Total commissions and fees	0	0
GCB | Insurance distribution revenue
Commissions and fees
Total commissions and fees	125	132
GCB | Insurance premiums
Commissions and fees
Total commissions and fees	43	47
GCB | Loan servicing
Commissions and fees
Total commissions and fees	11	22
GCB | Other
Commissions and fees
Total commissions and fees	56	62
Corporate/Other
Commissions and fees
Total commissions and fees	8	7
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	8	6
Corporate/Other | Other
Commissions and fees
Total commissions and fees	$ 0	$ 1