Cash Instruments - Cash Instruments by Level (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	$ 308,871	$ 295,952
Financial instruments sold, but not yet purchased, at fair value	(115,927)	(117,143)
Cash Instruments Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	257,494	235,815
Investments in funds measured at NAV	6,183	6,465
Total cash instrument assets	263,677	242,280
Cash Instruments Assets [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	151,632	135,366
Cash Instruments Assets [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	87,538	82,414
Cash Instruments Assets [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	18,324	18,035
Cash Instruments Assets [Member] | Money Market Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	1,735	1,319
Cash Instruments Assets [Member] | Money Market Instruments [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	307	188
Cash Instruments Assets [Member] | Money Market Instruments [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	1,428	1,131
Cash Instruments Assets [Member] | U.S. Government and Federal Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	71,035	57,657
Cash Instruments Assets [Member] | U.S. Government and Federal Agency Obligations [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	44,423	35,254
Cash Instruments Assets [Member] | U.S. Government and Federal Agency Obligations [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	26,612	22,403
Cash Instruments Assets [Member] | Non-U.S. Government and Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	35,614	29,381
Cash Instruments Assets [Member] | Non-U.S. Government and Agency Obligations [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	29,523	22,433
Cash Instruments Assets [Member] | Non-U.S. Government and Agency Obligations [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	6,061	6,933
Cash Instruments Assets [Member] | Non-U.S. Government and Agency Obligations [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	30	15
Cash Instruments Assets [Member] | Loans and Securities Backed by Commercial Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	3,602	3,842
Cash Instruments Assets [Member] | Loans and Securities Backed by Commercial Real Estate [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	1,998	2,197
Cash Instruments Assets [Member] | Loans and Securities Backed by Commercial Real Estate [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	1,604	1,645
Cash Instruments Assets [Member] | Loans and Securities Backed by Residential Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	12,133	12,195
Cash Instruments Assets [Member] | Loans and Securities Backed by Residential Real Estate [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	11,303	11,350
Cash Instruments Assets [Member] | Loans and Securities Backed by Residential Real Estate [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	830	845
Cash Instruments Assets [Member] | Corporate Loans And Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	31,721	28,659
Cash Instruments Assets [Member] | Corporate Loans And Debt Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	410	215
Cash Instruments Assets [Member] | Corporate Loans And Debt Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	26,758	23,804
Cash Instruments Assets [Member] | Corporate Loans And Debt Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	4,553	4,640
Cash Instruments Assets [Member] | State and Municipal Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	1,108	1,059
Cash Instruments Assets [Member] | State and Municipal Obligations [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	1,012	960
Cash Instruments Assets [Member] | State and Municipal Obligations [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	96	99
Cash Instruments Assets [Member] | Other Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	1,364	1,358
Cash Instruments Assets [Member] | Other Debt Obligations [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	868	830
Cash Instruments Assets [Member] | Other Debt Obligations [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	496	528
Cash Instruments Assets [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	95,539	94,692
Cash Instruments Assets [Member] | Equity Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	76,969	77,276
Cash Instruments Assets [Member] | Equity Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	7,855	7,153
Cash Instruments Assets [Member] | Equity Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	10,715	10,263
Cash Instruments Assets [Member] | Commodities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	3,643	5,653
Cash Instruments Assets [Member] | Commodities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	3,643	5,653
Cash Instruments Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value	(76,920)	(69,644)
Cash Instruments Liabilities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value	(67,267)	(61,522)
Cash Instruments Liabilities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value	(9,604)	(8,060)
Cash Instruments Liabilities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value	(49)	(62)
Cash Instruments Liabilities [Member] | U.S. Government and Federal Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value	(20,181)	(16,627)
Cash Instruments Liabilities [Member] | U.S. Government and Federal Agency Obligations [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value	(19,827)	(16,615)
Cash Instruments Liabilities [Member] | U.S. Government and Federal Agency Obligations [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value	(354)	(12)
Cash Instruments Liabilities [Member] | Non-U.S. Government and Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value	(23,285)	(20,502)
Cash Instruments Liabilities [Member] | Non-U.S. Government and Agency Obligations [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value	(21,532)	(19,137)
Cash Instruments Liabilities [Member] | Non-U.S. Government and Agency Obligations [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value	(1,753)	(1,364)
Cash Instruments Liabilities [Member] | Non-U.S. Government and Agency Obligations [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value		(1)
Cash Instruments Liabilities [Member] | Loans and Securities Backed by Residential Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value		(3)
Cash Instruments Liabilities [Member] | Loans and Securities Backed by Residential Real Estate [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value		(3)
Cash Instruments Liabilities [Member] | Corporate Loans And Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value	(7,258)	(6,570)
Cash Instruments Liabilities [Member] | Corporate Loans And Debt Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value	(8)	(2)
Cash Instruments Liabilities [Member] | Corporate Loans And Debt Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value	(7,208)	(6,524)
Cash Instruments Liabilities [Member] | Corporate Loans And Debt Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value	(42)	(44)
Cash Instruments Liabilities [Member] | Other Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value	(1)	(1)
Cash Instruments Liabilities [Member] | Other Debt Obligations [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value	(1)	(1)
Cash Instruments Liabilities [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value	(26,195)	(25,941)
Cash Instruments Liabilities [Member] | Equity Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value	(25,900)	(25,768)
Cash Instruments Liabilities [Member] | Equity Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value	(288)	(156)
Cash Instruments Liabilities [Member] | Equity Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value	$ (7)	$ (17)