Cash Instruments - Cash Instruments by Level (Parenthetical) (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	$ 292,420	$ 293,940
Cash Instruments Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	230,817	232,293
Level 2 [Member] | Cash Instruments Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	85,106	80,723
Level 2 [Member] | Cash Instruments Assets [Member] | CDOs and CLOs Backed by Real Estate and Corporate Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	374	405
Level 3 [Member] | Cash Instruments Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	18,141	18,131
Level 3 [Member] | Cash Instruments Assets [Member] | CDOs and CLOs Backed by Real Estate and Corporate Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	754	774
Level 3 [Member] | Cash Instruments Assets [Member] | Private Equity Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	8,550	7,690
Level 3 [Member] | Cash Instruments Assets [Member] | Real Estate Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	377	308
Level 3 [Member] | Cash Instruments Assets [Member] | Convertible Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned, at fair value	$ 449	$ 552