Balance sheet components (Details 6) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Goodwill And Intangible Assets Disclosure [Abstract]
Cost of goods sold	$ 836	$ 709	$ 2,512	$ 2,137
Operating expenses	447	378	1,344	1,136
Total	$ 1,283	$ 1,087	$ 3,856	$ 3,273