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	$ 55,959	$ 49,838
Less accumulated depreciation and amortization	(43,141)	(39,368)
Property and equipment, net of accumulated depreciation and amortization	12,818	10,470
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment	13,584	12,335
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment	28,752	27,565
Office equipment
Property, Plant and Equipment [Line Items]
Property and equipment	2,397	2,241
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment	3,969	3,411
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	$ 7,257	$ 4,286
Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Minimum | Computer equipment
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Minimum | Computer software
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Minimum | Office equipment
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Minimum | Furniture and fixtures
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	7 years
Maximum | Computer equipment
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Maximum | Computer software
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Maximum | Office equipment
Property, Plant and Equipment [Line Items]
Estimated useful life	7 years
Maximum | Furniture and fixtures
Property, Plant and Equipment [Line Items]
Estimated useful life	7 years