Collateralized Transactions (Offsetting of Certain Collateralized Transactions) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Securities Purchased under Agreements to Resell
Gross amounts	$ 262,976	$ 199,044
Amounts offset	(164,454)	(114,786)
Net amounts presented	98,522	84,258
Amounts not offset	(95,610)	(78,009)
Net amounts	2,912	6,249
Securities Borrowed
Gross amounts	134,711	133,431
Amounts offset	(18,398)	(9,421)
Net amounts presented	116,313	124,010
Amounts not offset	(112,551)	(119,358)
Net amounts	3,762	4,652
Securities Sold under Agreements to Repurchase
Gross amounts	214,213	171,210
Amounts offset	(164,454)	(114,786)
Net amounts presented	49,759	56,424
Amounts not offset	(41,095)	(48,067)
Net amounts	8,664	8,357
Securities Loaned
Gross amounts	30,306	23,014
Amounts offset	(18,398)	(9,422)
Net amounts presented	11,908	13,592
Amounts not offset	(11,677)	(13,271)
Net amounts	231	321
Not Subject to Legally Enforceable Master Netting Agreements
Securities purchased under agreements to resell	2,579	5,687
Securities borrowed	724	572
Securities sold under agreements to repurchase	6,762	6,945
Securities loaned	$ 191	$ 307