Geographic area information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Geographical area information [Abstract]
Net sales	$ 11,162	$ 11,686	$ 11,350	$ 11,550	$ 11,755	$ 15,838	$ 14,751	$ 12,243	$ 45,748	$ 54,587	$ 56,311
Fixed assets, net	2,244				2,272				2,244	2,272	2,169
United States [Member]
Geographical area information [Abstract]
Net sales									35,332	43,518	48,720
International [Member]
Geographical area information [Abstract]
Net sales									$ 10,416	$ 11,069	$ 7,591
Sales [Member] | Geographic Concentration Risk [Member] | International [Member]
Geographical area information [Abstract]
Concentration risk percentage									23.00%	20.00%	14.00%
Sales [Member] | Geographic Concentration Risk [Member] | Europe [Member]
Geographical area information [Abstract]
Concentration risk percentage									44.00%	56.00%	44.00%
Sales [Member] | Geographic Concentration Risk [Member] | Pacific Rim [Member]
Geographical area information [Abstract]
Concentration risk percentage									46.00%	36.00%	32.00%
Sales [Member] | Geographic Concentration Risk [Member] | Canada [Member]
Geographical area information [Abstract]
Concentration risk percentage									8.00%	6.00%	18.00%
Reportable Geographical Components [Member] | United States [Member]
Geographical area information [Abstract]
Net sales									$ 35,332	$ 43,518	$ 48,720
Fixed assets, net	1,326				1,767				1,326	1,767	1,548
Reportable Geographical Components [Member] | International [Member]
Geographical area information [Abstract]
Net sales									10,416	11,069	7,591
Fixed assets, net	$ 918				$ 505				$ 918	$ 505	$ 621