Earnings per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings per share [Abstract]
Net income	$ 384	$ 2,574	$ 1,316	$ 4,464
Shares [Abstract]
Basic: Weighted average common shares outstanding (in shares)	7,470	7,413	7,464	7,449
Add: Dilutive effect of outstanding options and restricted stock units as determined by the treasury stock method (in shares)	283	345	194	325
Diluted: Weighted average common and common equivalent shares outstanding (in shares)	7,753	7,758	7,658	7,774
Net income per common share [Abstract]
Basic (in dollars per share)	$ 0.05	$ 0.35	$ 0.18	$ 0.60
Diluted (in dollars per share)	$ 0.05	$ 0.33	$ 0.17	$ 0.57
Stock Awards [Member]
Earnings per share [Abstract]
Anti-dilutive securities excluded from computation of earnings per dilutive share (in shares)	326	147	462	149