Stockholders' Equity and Stock Based Compensation - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 1,135	$ 1,449	$ 4,252	$ 4,447
Product and content development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	174	382	1,271	1,451
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	289	338	1,012	1,065
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 672	$ 729	$ 1,969	$ 1,931