Earnings per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings per share [Abstract]
Net income	$ 186	$ 1,210	$ 932	$ 1,890
Shares [Abstract]
Basic: Weighted average common shares outstanding (in shares)	7,462	7,401	7,461	7,467
Add: Dilutive effect of outstanding options and restricted stock units as determined by the treasury stock method (in shares)	135	259	146	315
Diluted: Weighted average common and common equivalent shares outstanding (in shares)	7,597	7,660	7,607	7,782
Net income per common share [Abstract]
Basic (in dollars per share)	$ 0.02	$ 0.16	$ 0.12	$ 0.25
Diluted (in dollars per share)	$ 0.02	$ 0.16	$ 0.12	$ 0.24
Stock Awards [Member]
Earnings per share [Abstract]
Anti-dilutive securities excluded from computation of earnings per dilutive share (in shares)	542	196	542	147