Fixed Assets, Net - Components of Fixed Assets, Net (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Fixed assets, gross	$ 575,444	$ 562,702
Less: accumulated depreciation and amortization	(398,658)	(384,402)
Fixed assets, net	176,786	178,300
Computer and communications equipment
Property, Plant and Equipment [Line Items]
Fixed assets, gross	104,450	103,621
Software, including software development costs
Property, Plant and Equipment [Line Items]
Fixed assets, gross	371,636	360,047
Leasehold improvements and other fixed assets
Property, Plant and Equipment [Line Items]
Fixed assets, gross	$ 99,358	$ 99,034