Nature of Business and Summary of Significant Accounting Policies - Net Property and Equipment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 162,106	$ 135,046
Less: accumulated depreciation and amortization	(83,156)	(74,416)
Property and equipment, net	78,950	60,630
Computer and office equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 105,692	92,237
Computer and office equipment | Minimum
Property, Plant and Equipment [Line Items]
Property, plant & equipment useful lives	3 years
Computer and office equipment | Maximum
Property, Plant and Equipment [Line Items]
Property, plant & equipment useful lives	5 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant & equipment useful lives	Lesser of useful life of improvement or remaining life of lease
Property and equipment, gross	$ 33,093	19,380
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, plant & equipment useful lives	7 years
Property and equipment, gross	$ 11,145	11,304
Building and improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 10,391	10,340
Building and improvements | Minimum
Property, Plant and Equipment [Line Items]
Property, plant & equipment useful lives	7 years
Building and improvements | Maximum
Property, Plant and Equipment [Line Items]
Property, plant & equipment useful lives	30 years
Land
Property, Plant and Equipment [Line Items]
Property, plant & equipment useful lives	Non depreciable
Property and equipment, gross	$ 1,785	$ 1,785