Summary of Stock Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018		Jun. 30, 2017
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation before tax	$ 16,056	$ 13,932	$ 31,165	[1]	$ 26,440	[1]
Income tax benefit	(3,341)	(4,287)	(6,482)		(8,102)
Cost of revenue
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation before tax	4,257	3,677	7,958		7,299
Selling and marketing
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation before tax	6,038	4,101	10,696		7,506
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation before tax	3,802	3,575	7,439		6,887
General and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation before tax	$ 1,959	$ 2,579	$ 5,072		$ 4,748

[1] On January 1, 2018 the Company adopted the ASC 606 revenue recognition standard and has adjusted prior periods to conform. See Note 2. "New Accounting Pronouncements" for additional information.