Derivatives - Fair Values of Derivatives Reported on Condensed Consolidated Statements of Financial Condition (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Derivative Assets	$ 3,443	$ 1,993
Derivative Liabilities	189,142	182,223
Forward Foreign Currency Exchange Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets	2,938	1,993
Derivative Liabilities	3,835	2,792
Total Return Swaps and Other [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets	505
Derivative Liabilities	9,557	9,043
LFI and Other Similar Deferred Compensation Arrangements [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities	$ 175,750	$ 170,388