Stock Based Compensation - Stock Based Compensation Expense Recorded in Condensed Consolidated Statements of Income (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock based compensation expense	$ 1,938	$ 450	$ 2,347	$ 834
Cost of Revenues (Excluding Depreciation and Amortization) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock based compensation expense	738	23	761	40
Product Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock based compensation expense	413	53	458	97
Sales and Marketing [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock based compensation expense	372	56	426	103
Other General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock based compensation expense	$ 415	$ 318	$ 702	$ 594