COMMISSIONS AND FEES; ADMINISTRATION AND OTHER FIDUCIARY FEES - Administration and Other Fiduciary Fees (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Commissions and fees
Administration and other fiduciary fees	$ 3,411	$ 3,580	$ 3,584
Custody fees
Commissions and fees
Administration and other fiduciary fees	1,542	1,695	1,728
Fiduciary fees
Commissions and fees
Administration and other fiduciary fees	1,296	1,285	1,259
Guarantee fees
Commissions and fees
Administration and other fiduciary fees	573	600	597
Administration and other fiduciary fees
Commissions and fees
Administration and other fiduciary fees	3,411	3,580	3,584
Revenue not accounted for under ASC 606	573	600	597
ICG | Custody fees
Commissions and fees
Administration and other fiduciary fees	1,453	1,497	1,508
ICG | Fiduciary fees
Commissions and fees
Administration and other fiduciary fees	647	645	593
ICG | Guarantee fees
Commissions and fees
Administration and other fiduciary fees	558	584	584
ICG | Administration and other fiduciary fees
Commissions and fees
Administration and other fiduciary fees	2,658	2,726	2,685
GCB | Custody fees
Commissions and fees
Administration and other fiduciary fees	16	133	164
GCB | Fiduciary fees
Commissions and fees
Administration and other fiduciary fees	621	597	575
GCB | Guarantee fees
Commissions and fees
Administration and other fiduciary fees	8	9	5
GCB | Administration and other fiduciary fees
Commissions and fees
Administration and other fiduciary fees	645	739	744
Corporate/Other | Custody fees
Commissions and fees
Administration and other fiduciary fees	73	65	56
Corporate/Other | Fiduciary fees
Commissions and fees
Administration and other fiduciary fees	28	43	91
Corporate/Other | Guarantee fees
Commissions and fees
Administration and other fiduciary fees	7	7	8
Corporate/Other | Administration and other fiduciary fees
Commissions and fees
Administration and other fiduciary fees	$ 108	$ 115	$ 155