Stockholders' Equity and Stock Based Compensation - Stock-based Compensation Expense (Details) - 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 [Line Items]
Stock-based compensation expense	$ 1,637	$ 1,810	$ 3,117	$ 2,998
Product and content development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	513	626	1,097	1,069
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	353	488	723	727
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 771	$ 696	$ 1,297	$ 1,202