Derivatives - Fair Values of Derivatives Reported on Condensed Consolidated Statements of Financial Condition (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Derivative Assets	$ 12,210	$ 2,355
Derivative Liabilities	189,563	208,093
Forward Foreign Currency Exchange Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets	876	2,355
Derivative Liabilities	926	124
Total Return Swaps and Other [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets	11,334
Derivative Liabilities		663
LFI and Other Similar Deferred Compensation Arrangements [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities	$ 188,637	$ 207,306