Stock Based Compensation Expense Included in Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation before tax	$ 10,818	$ 8,091	$ 30,634	$ 23,005
Income tax benefit	(3,227)	(2,326)	(8,917)	(6,437)
Cost of revenue
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation before tax	3,117	2,285	8,711	6,519
Operating Expenses
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation before tax	$ 7,701	$ 5,806	$ 21,923	$ 16,486