COMMISSIONS AND FEES; ADMINISTRATION AND OTHER FIDUCIARY FEES - Commissions and Fees Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Commissions and fees
Commissions and fees revenue	$ 11,857	$ 12,707	$ 11,678
Investment banking
Commissions and fees
Commissions and fees revenue	3,568	3,817	3,000
Brokerage commissions
Commissions and fees
Commissions and fees revenue	2,792	2,718	2,395
Credit- and bank-card income, interchange fees
Commissions and fees
Commissions and fees revenue	9,200	8,575	7,190
Credit- and bank-card income, card-related loan fees
Commissions and fees
Commissions and fees revenue	702	794	876
Credit- and bank-card income, card rewards and partner payments
Commissions and fees
Commissions and fees revenue	(8,769)	(7,725)	(6,556)
Deposit-related fees
Commissions and fees
Commissions and fees revenue	1,604	1,687	1,558
Transactional service fees
Commissions and fees
Commissions and fees revenue	820	878	920
Corporate finance
Commissions and fees
Commissions and fees revenue	734	766	745
Insurance distribution revenue
Commissions and fees
Commissions and fees revenue	590	642	684
Insurance premiums
Commissions and fees
Commissions and fees revenue	119	122	280
Loan servicing
Commissions and fees
Commissions and fees revenue	315	342	351
Other
Commissions and fees
Commissions and fees revenue	182	91	235
Overdraft fees
Commissions and fees
Commissions and fees revenue	128	135	133
Commissions and fees
Commissions and fees
Revenue not accounted for under ASC 606	(6,766)	(5,568)	(4,169)
ICG
Commissions and fees
Commissions and fees revenue	8,768	8,850	7,698
ICG | Investment banking
Commissions and fees
Commissions and fees revenue	3,568	3,817	3,000
ICG | Brokerage commissions
Commissions and fees
Commissions and fees revenue	1,977	1,889	1,748
ICG | Credit- and bank-card income, interchange fees
Commissions and fees
Commissions and fees revenue	1,072	950	837
ICG | Credit- and bank-card income, card-related loan fees
Commissions and fees
Commissions and fees revenue	63	53	27
ICG | Credit- and bank-card income, card rewards and partner payments
Commissions and fees
Commissions and fees revenue	(503)	(425)	(361)
ICG | Deposit-related fees
Commissions and fees
Commissions and fees revenue	949	947	818
ICG | Transactional service fees
Commissions and fees
Commissions and fees revenue	718	738	700
ICG | Corporate finance
Commissions and fees
Commissions and fees revenue	729	761	741
ICG | Insurance distribution revenue
Commissions and fees
Commissions and fees revenue	14	12	10
ICG | Insurance premiums
Commissions and fees
Commissions and fees revenue	0	0	0
ICG | Loan servicing
Commissions and fees
Commissions and fees revenue	156	146	147
ICG | Other
Commissions and fees
Commissions and fees revenue	25	(38)	31
GCB
Commissions and fees
Commissions and fees revenue	3,011	3,508	3,271
GCB | Investment banking
Commissions and fees
Commissions and fees revenue	0	0	0
GCB | Brokerage commissions
Commissions and fees
Commissions and fees revenue	815	826	636
GCB | Credit- and bank-card income, interchange fees
Commissions and fees
Commissions and fees revenue	8,117	7,526	6,189
GCB | Credit- and bank-card income, card-related loan fees
Commissions and fees
Commissions and fees revenue	627	693	784
GCB | Credit- and bank-card income, card rewards and partner payments
Commissions and fees
Commissions and fees revenue	(8,254)	(7,243)	(6,084)
GCB | Deposit-related fees
Commissions and fees
Commissions and fees revenue	654	726	721
GCB | Transactional service fees
Commissions and fees
Commissions and fees revenue	98	91	84
GCB | Corporate finance
Commissions and fees
Commissions and fees revenue	5	5	4
GCB | Insurance distribution revenue
Commissions and fees
Commissions and fees revenue	565	562	584
GCB | Insurance premiums
Commissions and fees
Commissions and fees revenue	119	122	136
GCB | Loan servicing
Commissions and fees
Commissions and fees revenue	122	101	127
GCB | Other
Commissions and fees
Commissions and fees revenue	143	99	90
Corporate/Other
Commissions and fees
Commissions and fees revenue	78	349	709
Corporate/Other | Investment banking
Commissions and fees
Commissions and fees revenue	0	0	0
Corporate/Other | Brokerage commissions
Commissions and fees
Commissions and fees revenue	0	3	11
Corporate/Other | Credit- and bank-card income, interchange fees
Commissions and fees
Commissions and fees revenue	11	99	164
Corporate/Other | Credit- and bank-card income, card-related loan fees
Commissions and fees
Commissions and fees revenue	12	48	65
Corporate/Other | Credit- and bank-card income, card rewards and partner payments
Commissions and fees
Commissions and fees revenue	(12)	(57)	(111)
Corporate/Other | Deposit-related fees
Commissions and fees
Commissions and fees revenue	1	14	19
Corporate/Other | Transactional service fees
Commissions and fees
Commissions and fees revenue	4	49	136
Corporate/Other | Corporate finance
Commissions and fees
Commissions and fees revenue	0	0	0
Corporate/Other | Insurance distribution revenue
Commissions and fees
Commissions and fees revenue	11	68	90
Corporate/Other | Insurance premiums
Commissions and fees
Commissions and fees revenue	0	0	144
Corporate/Other | Loan servicing
Commissions and fees
Commissions and fees revenue	37	95	77
Corporate/Other | Other
Commissions and fees
Commissions and fees revenue	$ 14	$ 30	$ 114