Summary of significant accounting policies, Revenue recognition - Disaggregation of revenue (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
Summary of significant accounting policies [Abstract]
Term of free maintenance upon completion of software installation									1 year
Disaggregation of revenue [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
United States [Member]
Disaggregation of revenue [Abstract]
Net sales									35,332	43,518	48,720
International [Member]
Disaggregation of revenue [Abstract]
Net sales									10,416	11,069	7,591
Food Service Technology [Member]
Disaggregation of revenue [Abstract]
Net sales									6,104	5,086	4,862
Food Service Technology [Member] | United States [Member]
Disaggregation of revenue [Abstract]
Net sales									5,522	4,640	4,488
Food Service Technology [Member] | International [Member]
Disaggregation of revenue [Abstract]
Net sales									582	446	374
POS Automation and Banking [Member]
Disaggregation of revenue [Abstract]
Net sales									5,758	7,273	7,905
POS Automation and Banking [Member] | United States [Member]
Disaggregation of revenue [Abstract]
Net sales									5,714	7,122	7,596
POS Automation and Banking [Member] | International [Member]
Disaggregation of revenue [Abstract]
Net sales									44	151	309
Casino and Gaming [Member]
Disaggregation of revenue [Abstract]
Net sales									21,529	26,593	18,615
Casino and Gaming [Member] | United States [Member]
Disaggregation of revenue [Abstract]
Net sales									13,076	17,518	13,608
Casino and Gaming [Member] | International [Member]
Disaggregation of revenue [Abstract]
Net sales									8,453	9,075	5,007
Lottery [Member]
Disaggregation of revenue [Abstract]
Net sales									1,291	3,093	9,805
Lottery [Member] | United States [Member]
Disaggregation of revenue [Abstract]
Net sales									1,290	3,046	8,626
Lottery [Member] | International [Member]
Disaggregation of revenue [Abstract]
Net sales									1	47	1,179
Printrex [Member]
Disaggregation of revenue [Abstract]
Net sales									1,166	1,297	1,052
Printrex [Member] | United States [Member]
Disaggregation of revenue [Abstract]
Net sales									961	1,028	849
Printrex [Member] | International [Member]
Disaggregation of revenue [Abstract]
Net sales									205	269	203
TransAct Services Group [Member]
Disaggregation of revenue [Abstract]
Net sales									9,900	11,245	14,072
TransAct Services Group [Member] | United States [Member]
Disaggregation of revenue [Abstract]
Net sales									8,769	10,164	13,553
TransAct Services Group [Member] | International [Member]
Disaggregation of revenue [Abstract]
Net sales									$ 1,131	$ 1,081	$ 519