Segment and Geographic Information (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 and Geographic Information
Number of operating segments			1
Number of reportable segments			1
Segment and geographic information
Revenue	$ 35,267	$ 30,174	$ 95,497	$ 72,652
Domestic
Segment and geographic information
Revenue	34,517	29,224	93,221	69,480
International
Segment and geographic information
Revenue	$ 750	$ 950	$ 2,276	$ 3,172