Amortization Expense of Acquired Intangibles (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Acquired Finite-Lived Intangible Assets [Line Items]
Total amortization expense	$ 3,599	$ 2,979	$ 10,168	$ 9,236
Cost of revenue
Acquired Finite-Lived Intangible Assets [Line Items]
Total amortization expense	1,642	1,351	4,626	4,041
Selling and marketing
Acquired Finite-Lived Intangible Assets [Line Items]
Total amortization expense	1,867	1,537	5,274	4,602
General and administrative
Acquired Finite-Lived Intangible Assets [Line Items]
Total amortization expense	$ 90	$ 91	$ 268	$ 593