Geographic Information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Geographic Information
Total revenue	$ 7,064	$ 7,164	$ 6,659	$ 6,207	$ 6,800	$ 7,092	$ 6,349	$ 6,305	$ 27,094	$ 26,546	$ 24,896
United States
Geographic Information
Total revenue									4,321	5,362	6,055
Singapore
Geographic Information
Total revenue									5,467	4,614	3,399
Japan
Geographic Information
Total revenue									3,285	2,280	4,408
Germany
Geographic Information
Total revenue									3,013	3,546	2,933
Taiwan
Geographic Information
Total revenue									2,161	3,759	3,097
Hong Kong
Geographic Information
Total revenue									2,122	2,744	3,133
All other
Geographic Information
Total revenue									$ 6,725	$ 4,241	$ 1,871