Segment Information and Revenues by Product Category (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 item	Sep. 30, 2012
Segment Information and Revenues by Product Category
Number of reportable operating segments			1
Categories of products or services			2
Segment information and revenues by product category
Total revenue	$ 58,825	$ 49,446	$ 170,553	$ 146,496
Consumer advertising
Segment information and revenues by product category
Total revenue	45,630	40,113	132,348	120,661
Software and services
Segment information and revenues by product category
Total revenue	$ 13,195	$ 9,333	$ 38,205	$ 25,835