COMMISSIONS AND FEES; ADMINISTRATION AND OTHER FIDUCIARY FEES - Commissions and Fees Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Commissions and fees
Total commissions and fees	$ 2,753	$ 2,906	$ 8,707	$ 8,713
Investment banking
Commissions and fees
Total commissions and fees	1,076	900	3,474	2,755
Brokerage commissions
Commissions and fees
Total commissions and fees	746	684	2,258	1,990
Interchange fees
Commissions and fees
Total commissions and fees	2,000	2,505	5,806	7,278
Card-related loan fees
Commissions and fees
Total commissions and fees	161	206	473	578
Card rewards and partner payments
Commissions and fees
Total commissions and fees	(2,146)	(2,444)	(6,203)	(7,110)
Deposit-related fees
Commissions and fees
Total commissions and fees	325	391	978	1,161
Transactional service fees
Commissions and fees
Total commissions and fees	237	224	723	684
Corporate finance
Commissions and fees
Total commissions and fees	77	129	372	459
Insurance distribution revenue
Commissions and fees
Total commissions and fees	133	141	376	408
Insurance premiums
Commissions and fees
Total commissions and fees	25	41	99	133
Loan servicing
Commissions and fees
Total commissions and fees	30	19	100	108
Other
Commissions and fees
Total commissions and fees	89	110	251	269
Overdraft fees
Commissions and fees
Total commissions and fees	23	33	74	94
Commissions and fees
Commissions and fees
Revenue not accounted for under ASC 606, revenue from contracts with customers	(1,816)	(2,009)	(5,044)	(5,728)
ICG
Commissions and fees
Total commissions and fees	2,245	2,144	7,171	6,546
ICG | Investment banking
Commissions and fees
Total commissions and fees	1,076	900	3,474	2,755
ICG | Brokerage commissions
Commissions and fees
Total commissions and fees	486	456	1,545	1,365
ICG | Interchange fees
Commissions and fees
Total commissions and fees	158	326	542	919
ICG | Card-related loan fees
Commissions and fees
Total commissions and fees	4	15	18	44
ICG | Card rewards and partner payments
Commissions and fees
Total commissions and fees	(73)	(192)	(292)	(520)
ICG | Deposit-related fees
Commissions and fees
Total commissions and fees	246	272	699	800
ICG | Transactional service fees
Commissions and fees
Total commissions and fees	217	194	659	594
ICG | Corporate finance
Commissions and fees
Total commissions and fees	77	129	372	459
ICG | Insurance distribution revenue
Commissions and fees
Total commissions and fees	4	4	9	10
ICG | Insurance premiums
Commissions and fees
Total commissions and fees	0	0	0	0
ICG | Loan servicing
Commissions and fees
Total commissions and fees	16	1	54	51
ICG | Other
Commissions and fees
Total commissions and fees	34	39	91	69
GCB
Commissions and fees
Total commissions and fees	498	754	1,513	2,149
GCB | Investment banking
Commissions and fees
Total commissions and fees	0	0	0	0
GCB | Brokerage commissions
Commissions and fees
Total commissions and fees	260	228	713	625
GCB | Interchange fees
Commissions and fees
Total commissions and fees	1,842	2,179	5,264	6,359
GCB | Card-related loan fees
Commissions and fees
Total commissions and fees	157	191	455	534
GCB | Card rewards and partner payments
Commissions and fees
Total commissions and fees	(2,073)	(2,252)	(5,911)	(6,590)
GCB | Deposit-related fees
Commissions and fees
Total commissions and fees	79	119	279	361
GCB | Transactional service fees
Commissions and fees
Total commissions and fees	20	30	64	90
GCB | Corporate finance
Commissions and fees
Total commissions and fees	0	0	0	0
GCB | Insurance distribution revenue
Commissions and fees
Total commissions and fees	129	137	367	398
GCB | Insurance premiums
Commissions and fees
Total commissions and fees	25	41	99	133
GCB | Loan servicing
Commissions and fees
Total commissions and fees	4	11	26	41
GCB | Other
Commissions and fees
Total commissions and fees	55	70	157	198
Corporate/Other
Commissions and fees
Total commissions and fees	10	8	23	18
Corporate/Other | Investment banking
Commissions and fees
Total commissions and fees	0	0	0	0
Corporate/Other | Brokerage commissions
Commissions and fees
Total commissions and fees	0	0	0	0
Corporate/Other | Interchange fees
Commissions and fees
Total commissions and fees	0	0	0	0
Corporate/Other | Card-related loan fees
Commissions and fees
Total commissions and fees	0	0	0	0
Corporate/Other | Card rewards and partner payments
Commissions and fees
Total commissions and fees	0	0	0	0
Corporate/Other | Deposit-related fees
Commissions and fees
Total commissions and fees	0	0	0	0
Corporate/Other | Transactional service fees
Commissions and fees
Total commissions and fees	0	0	0	0
Corporate/Other | Corporate finance
Commissions and fees
Total commissions and fees	0	0	0	0
Corporate/Other | Insurance distribution revenue
Commissions and fees
Total commissions and fees	0	0	0	0
Corporate/Other | Insurance premiums
Commissions and fees
Total commissions and fees	0	0	0	0
Corporate/Other | Loan servicing
Commissions and fees
Total commissions and fees	10	7	20	16
Corporate/Other | Other
Commissions and fees
Total commissions and fees	$ 0	$ 1	$ 3	$ 2