Collateralized Transactions - Offsetting of Certain Collateralized Transactions (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Securities purchased under agreements to resell
Gross amounts	$ 250,004	$ 262,976
Amounts offset	(164,606)	(164,454)
Net amounts presented	85,398	98,522
Amounts not offset	(83,492)	(95,610)
Net amounts	1,906	2,912
Securities borrowed
Gross amounts	143,046	134,711
Amounts offset	(9,466)	(18,398)
Net amounts presented	133,580	116,313
Amounts not offset	(129,614)	(112,551)
Net amounts	3,966	3,762
Securities sold under agreements to repurchase
Gross amounts	226,900	214,213
Amounts offset	(164,606)	(164,454)
Net amounts presented	62,294	49,759
Amounts not offset	(53,942)	(41,095)
Net amounts	8,352	8,664
Securities loaned
Gross amounts	19,791	30,306
Amounts offset	(9,466)	(18,398)
Net amounts presented	10,325	11,908
Amounts not offset	(10,298)	(11,677)
Net amounts	27	231
Net amounts for which master netting agreements are not in place or may not be legally enforceable
Securities purchased under agreements to resell	1,425	2,579
Securities borrowed	828	724
Securities sold under agreements to repurchase	6,603	6,762
Securities loaned	$ 17	$ 191