Fair Value Option - Financial Assets and Financial Liabilities by Level (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities segregated for regulatory and other purposes	$ 36,058	$ 38,504
Securities purchased under agreements to resell	93,352	119,450
Securities borrowed	78,788	69,801
Receivables from customers and counterparties	3,297	4,992
Total financial assets at fair value	211,495	232,747
Deposits	(14,096)	(14,680)
Securities sold under agreements to repurchase	(73,905)	(86,069)
Securities loaned	(1,969)	(466)
Other secured financings	(22,006)	(23,207)
Unsecured borrowings Short-term	(16,741)	(17,743)
Unsecured borrowings Long-term	(30,266)	(22,273)
Other liabilities and accrued expenses	(665)	(1,253)
Total financial liabilities at fair value	(159,648)	(165,691)
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities segregated for regulatory and other purposes	19,186	19,562
Total financial assets at fair value	19,186	19,562
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities segregated for regulatory and other purposes	16,872	18,942
Securities purchased under agreements to resell	93,352	119,450
Securities borrowed	78,788	69,801
Receivables from customers and counterparties	3,242	4,947
Total financial assets at fair value	192,254	213,140
Deposits	(10,878)	(12,465)
Securities sold under agreements to repurchase	(73,830)	(85,998)
Securities loaned	(1,969)	(466)
Other secured financings	(21,390)	(22,658)
Unsecured borrowings Short-term	(13,069)	(13,610)
Unsecured borrowings Long-term	(22,828)	(18,049)
Other liabilities and accrued expenses	(556)	(1,201)
Total financial liabilities at fair value	(144,520)	(154,447)
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Receivables from customers and counterparties	55	45
Total financial assets at fair value	55	45
Deposits	(3,218)	(2,215)
Securities sold under agreements to repurchase	(75)	(71)
Other secured financings	(616)	(549)
Unsecured borrowings Short-term	(3,672)	(4,133)
Unsecured borrowings Long-term	(7,438)	(4,224)
Other liabilities and accrued expenses	(109)	(52)
Total financial liabilities at fair value	$ (15,128)	$ (11,244)