Segments Schedule of revenue by geographic region (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 25,968	$ 20,401	$ 73,965	$ 57,797
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	23,332	18,770	65,502	53,049
International
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 2,636	$ 1,631	$ 8,463	$ 4,748