Financial Instruments Owned, at Fair Value and Financial Instruments Sold, But Not Yet Purchased, at Fair Value - Gains and Losses from Market Making and Other Principal Transactions (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Financial Instruments Owned and Pledged as Collateral [Line Items]
Market making	$ 2,715	$ 1,730	$ 7,067	$ 7,964
Other principal transactions	1,163	543	1,978	3,822
Trading Activity, Gains and Losses, Net	3,878	2,273	9,045	11,786
Interest Rates [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Market making	821	(132)	1,091	146
Credit [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Market making	440	298	1,688	1,218
Foreign Exchange [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Market making	544	(656)	1,254	1,135
Equities [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Market making	663	1,968	2,215	4,671
Commodities [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Market making	$ 247	$ 252	$ 819	$ 794