COMMISSIONS AND FEES; ADMINISTRATION AND OTHER FIDUCIARY FEES - Commissions and Fees Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Commissions and fees
Commissions and fees	$ 2,881	$ 3,111	$ 5,807	$ 6,141
Investment banking
Commissions and fees
Commissions and fees	934	1,012	1,844	1,834
Brokerage commissions
Commissions and fees
Commissions and fees	649	697	1,306	1,511
Interchange fees
Commissions and fees
Commissions and fees	2,511	2,306	4,773	4,445
Card-related loan fees
Commissions and fees
Commissions and fees	199	170	372	345
Card rewards and partner payments
Commissions and fees
Commissions and fees	(2,451)	(2,197)	(4,665)	(4,200)
Deposit-related fees
Commissions and fees
Commissions and fees	385	397	769	817
Transactional service fees
Commissions and fees
Commissions and fees	230	204	460	417
Corporate finance
Commissions and fees
Commissions and fees	151	220	330	363
Insurance distribution revenue
Commissions and fees
Commissions and fees	131	152	267	305
Insurance premiums
Commissions and fees
Commissions and fees	27	33	55	65
Loan servicing
Commissions and fees
Commissions and fees	19	82	97	154
Other
Commissions and fees
Commissions and fees	96	35	199	85
Overdraft fees
Commissions and fees
Commissions and fees	31	30	61	62
Commissions and fees
Commissions and fees
Revenue not accounted for under ASC 606, Revenue from Contracts with Customers	(2,025)	(1,648)	(3,746)	(3,193)
ICG
Commissions and fees
Commissions and fees	2,122	2,345	4,322	4,509
ICG | Investment banking
Commissions and fees
Commissions and fees	934	1,012	1,844	1,834
ICG | Brokerage commissions
Commissions and fees
Commissions and fees	438	491	909	1,057
ICG | Interchange fees
Commissions and fees
Commissions and fees	313	276	591	536
ICG | Card-related loan fees
Commissions and fees
Commissions and fees	16	17	29	31
ICG | Card rewards and partner payments
Commissions and fees
Commissions and fees	(174)	(126)	(327)	(250)
ICG | Deposit-related fees
Commissions and fees
Commissions and fees	247	236	492	472
ICG | Transactional service fees
Commissions and fees
Commissions and fees	194	182	389	372
ICG | Corporate finance
Commissions and fees
Commissions and fees	150	219	328	361
ICG | Insurance distribution revenue
Commissions and fees
Commissions and fees	2	5	6	10
ICG | Insurance premiums
Commissions and fees
Commissions and fees	0	0	0	0
ICG | Loan servicing
Commissions and fees
Commissions and fees	0	33	42	71
ICG | Other
Commissions and fees
Commissions and fees	2	0	19	15
GCB
Commissions and fees
Commissions and fees	755	743	1,475	1,582
GCB | Investment banking
Commissions and fees
Commissions and fees	0	0	0	0
GCB | Brokerage commissions
Commissions and fees
Commissions and fees	211	206	397	454
GCB | Interchange fees
Commissions and fees
Commissions and fees	2,198	2,025	4,182	3,899
GCB | Card-related loan fees
Commissions and fees
Commissions and fees	183	147	343	302
GCB | Card rewards and partner payments
Commissions and fees
Commissions and fees	(2,277)	(2,065)	(4,338)	(3,939)
GCB | Deposit-related fees
Commissions and fees
Commissions and fees	138	160	277	343
GCB | Transactional service fees
Commissions and fees
Commissions and fees	36	21	71	42
GCB | Corporate finance
Commissions and fees
Commissions and fees	1	1	2	2
GCB | Insurance distribution revenue
Commissions and fees
Commissions and fees	129	142	261	285
GCB | Insurance premiums
Commissions and fees
Commissions and fees	26	32	55	65
GCB | Loan servicing
Commissions and fees
Commissions and fees	16	40	46	62
GCB | Other
Commissions and fees
Commissions and fees	94	34	179	67
Corporate/Other
Commissions and fees
Commissions and fees	4	23	10	50
Corporate/Other | Investment banking
Commissions and fees
Commissions and fees	0	0	0	0
Corporate/Other | Brokerage commissions
Commissions and fees
Commissions and fees	0	0	0	0
Corporate/Other | Interchange fees
Commissions and fees
Commissions and fees	0	5	0	10
Corporate/Other | Card-related loan fees
Commissions and fees
Commissions and fees	0	6	0	12
Corporate/Other | Card rewards and partner payments
Commissions and fees
Commissions and fees	0	(6)	0	(11)
Corporate/Other | Deposit-related fees
Commissions and fees
Commissions and fees	0	1	0	2
Corporate/Other | Transactional service fees
Commissions and fees
Commissions and fees	0	1	0	3
Corporate/Other | Corporate finance
Commissions and fees
Commissions and fees	0	0	0	0
Corporate/Other | Insurance distribution revenue
Commissions and fees
Commissions and fees	0	5	0	10
Corporate/Other | Insurance premiums
Commissions and fees
Commissions and fees	1	1	0	0
Corporate/Other | Loan servicing
Commissions and fees
Commissions and fees	3	9	9	21
Corporate/Other | Other
Commissions and fees
Commissions and fees	$ 0	$ 1	$ 1	$ 3