COMMISSIONS AND FEES; ADMINISTRATION AND OTHER FIDUCIARY FEES - Administration and Other Fiduciary Fees (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Commissions and fees
Administration and other fiduciary fees	$ 905	$ 834
Revenue not accounted for under ASC 606, Revenue from Contracts with Customers	153	143
Institutional Clients Group
Commissions and fees
Administration and other fiduciary fees	672	624
Global Consumer Banking
Commissions and fees
Administration and other fiduciary fees	208	184
Corporate/Other
Commissions and fees
Administration and other fiduciary fees	25	26
Custody fees
Commissions and fees
Administration and other fiduciary fees	431	406
Custody fees | Institutional Clients Group
Commissions and fees
Administration and other fiduciary fees	368	355
Custody fees | Global Consumer Banking
Commissions and fees
Administration and other fiduciary fees	47	38
Custody fees | Corporate/Other
Commissions and fees
Administration and other fiduciary fees	16	13
Fiduciary fees
Commissions and fees
Administration and other fiduciary fees	321	285
Fiduciary fees | Institutional Clients Group
Commissions and fees
Administration and other fiduciary fees	167	141
Fiduciary fees | Global Consumer Banking
Commissions and fees
Administration and other fiduciary fees	147	133
Fiduciary fees | Corporate/Other
Commissions and fees
Administration and other fiduciary fees	7	11
Guarantee fees
Commissions and fees
Administration and other fiduciary fees	153	143
Guarantee fees | Institutional Clients Group
Commissions and fees
Administration and other fiduciary fees	137	128
Guarantee fees | Global Consumer Banking
Commissions and fees
Administration and other fiduciary fees	14	13
Guarantee fees | Corporate/Other
Commissions and fees
Administration and other fiduciary fees	$ 2	$ 2