COMMISSIONS AND FEES; ADMINISTRATION AND OTHER FIDUCIARY FEES - Administration and Other Fiduciary Fees (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Commissions and fees
Administration and other fiduciary fees	[1]	$ 3,580	$ 3,584	$ 3,294
Custody fees
Commissions and fees
Administration and other fiduciary fees		1,695	1,728	1,564
Fiduciary fees
Commissions and fees
Administration and other fiduciary fees		1,285	1,259	1,143
Guarantee fees
Commissions and fees
Administration and other fiduciary fees		600	597	587
Administration and other fiduciary fees
Commissions and fees
Administration and other fiduciary fees		3,580	3,584	3,294
Revenue not accounted for under ASC 606		600	597	587
ICG | Custody fees
Commissions and fees
Administration and other fiduciary fees		1,494	1,505	1,353
ICG | Fiduciary fees
Commissions and fees
Administration and other fiduciary fees		645	593	554
ICG | Guarantee fees
Commissions and fees
Administration and other fiduciary fees		536	535	523
ICG | Administration and other fiduciary fees
Commissions and fees
Administration and other fiduciary fees		2,675	2,633	2,430
GCB | Custody fees
Commissions and fees
Administration and other fiduciary fees		136	167	163
GCB | Fiduciary fees
Commissions and fees
Administration and other fiduciary fees		597	575	539
GCB | Guarantee fees
Commissions and fees
Administration and other fiduciary fees		57	54	54
GCB | Administration and other fiduciary fees
Commissions and fees
Administration and other fiduciary fees		790	796	756
Corporate/Other | Custody fees
Commissions and fees
Administration and other fiduciary fees		65	56	48
Corporate/Other | Fiduciary fees
Commissions and fees
Administration and other fiduciary fees		43	91	50
Corporate/Other | Guarantee fees
Commissions and fees
Administration and other fiduciary fees		7	8	10
Corporate/Other | Administration and other fiduciary fees
Commissions and fees
Administration and other fiduciary fees		$ 115	$ 155	$ 108

[1] Certain prior-period revenue and expense lines and totals were reclassified to conform to the current period’s presentation. See Notes 1 and 3 to the Consolidated Financial Statements.