Capitalized Software, Furniture, Equipment and Leasehold Improvements - Capitalized Software Development Costs, Furniture, Equipment and Leasehold Improvements, Net of Accumulated Depreciation and Amortization (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Furniture, equipment, leasehold improvements and capitalized software, Gross	$ 276,991	$ 248,759
Accumulated depreciation and amortization	(180,930)	(163,555)
Furniture, equipment, leasehold improvements and capitalized software, net of accumulated depreciation and amortization	96,061	85,204
Software Development Costs [Member]
Property, Plant and Equipment [Line Items]
Furniture, equipment, leasehold improvements and capitalized software, Gross	183,998	151,139
Computer Hardware and Related Software [Member]
Property, Plant and Equipment [Line Items]
Furniture, equipment, leasehold improvements and capitalized software, Gross	45,986	52,696
Office Hardware [Member]
Property, Plant and Equipment [Line Items]
Furniture, equipment, leasehold improvements and capitalized software, Gross	8,866	8,782
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Furniture, equipment, leasehold improvements and capitalized software, Gross	7,120	7,078
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Furniture, equipment, leasehold improvements and capitalized software, Gross	$ 31,021	$ 29,064