Earnings per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings per share [Abstract]
Net income	$ 746	$ 680
Shares [Abstract]
Basic: Weighted average common shares outstanding (in shares)	7,461	7,533
Add: Dilutive effect of outstanding options and restricted stock units as determined by the treasury stock method (in shares)	158	368
Diluted: Weighted average common and common equivalent shares outstanding (in shares)	7,619	7,901
Net income per common share [Abstract]
Basic (in dollars per share)	$ 0.10	$ 0.09
Diluted (in dollars per share)	$ 0.10	$ 0.09
Stock Awards [Member]
Earnings per share [Abstract]
Anti-dilutive securities excluded from computation of earnings per dilutive share (in shares)	540	147