Geographic area information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net sales [Abstract]
Net sales	$ 13,603	$ 14,474	$ 14,801	$ 14,357	$ 12,116	$ 14,172	$ 17,224	$ 16,164	$ 57,235	$ 59,676	$ 53,108
Fixed assets, net [Abstract]
Fixed assets, net	2,507				2,438				$ 2,241	$ 2,507	$ 2,438
International [Member]
Fixed assets, net [Abstract]
Concentration risk percentage									20.00%	23.00%	27.00%
Europe [Member]
Fixed assets, net [Abstract]
Concentration risk percentage									56.00%	56.00%	49.00%
Pacific Rim [Member]
Fixed assets, net [Abstract]
Concentration risk percentage									34.00%	34.00%	33.00%
Canada [Member]
Fixed assets, net [Abstract]
Concentration risk percentage									8.00%	8.00%	5.00%
Reportable Geographical Components [Member] | United States [Member]
Net sales [Abstract]
Net sales									$ 45,542	$ 45,730	$ 38,567
Fixed assets, net [Abstract]
Fixed assets, net	1,769				1,490				1,581	1,769	1,490
Reportable Geographical Components [Member] | International [Member]
Net sales [Abstract]
Net sales									11,693	13,946	14,541
Fixed assets, net [Abstract]
Fixed assets, net	$ 738				$ 948				$ 660	$ 738	$ 948