Segment and Geographic Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 item	Jun. 30, 2012
Segment and Geographic Information
Number of operating segments			1
Number of reportable segments			1
Segment and geographic information
Revenue	$ 35,465	$ 25,206	$ 60,230	$ 42,478
Domestic
Segment and geographic information
Revenue	34,785	24,067	58,704	40,256
International
Segment and geographic information
Revenue	$ 680	$ 1,139	$ 1,526	$ 2,222