Derivatives - Fair Values of Derivatives Reported on Consolidated Statements of Financial Condition (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Total Derivative Assets	$ 536	$ 1,395
Derivative Liabilities	314,485	236,273
Forward Foreign Currency Exchange Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Total Derivative Assets	536	1,395
Derivative Liabilities	333	1,720
Total Return Swaps and Other [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities	2,752	8,527
LFI and Other Similar Deferred Compensation Arrangements [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities	$ 311,400	$ 226,026