Fixed Assets, Net - Components of Fixed Assets, Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Fixed assets, gross	$ 507,240	$ 482,374
Less: accumulated depreciation and amortization	(325,161)	(292,262)
Fixed assets, net	182,079	190,112
Computer and communications equipment
Property, Plant and Equipment [Line Items]
Fixed assets, gross	100,527	96,472
Software, including software development costs
Property, Plant and Equipment [Line Items]
Fixed assets, gross	309,627	280,540
Leasehold improvements and other fixed assets
Property, Plant and Equipment [Line Items]
Fixed assets, gross	$ 97,086	$ 105,362