Property and Equipment (Capital Lease Obligations) (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 135,846	$ 133,262
Capital leases, gross	78,444	78,923
Less: accumulated depreciation and amortization (including capital leases of $70,530 and $58,874, respectively)	(106,953)	(91,261)
Less: accumulated depreciation, capital leases	70,530	58,874
Property and equipment, net	28,893	42,001
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	106,433	100,322
Capital leases, gross	77,606	78,113
Computer Software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	8,061	8,192
Internal software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,323	2,323
Office equipment and furniture
Property, Plant and Equipment [Line Items]
Property and equipment, gross	5,478	5,877
Automobiles
Property, Plant and Equipment [Line Items]
Property and equipment, gross	838	810
Capital leases, gross	838	810
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 15,036	$ 18,061