Earnings per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share, Basic and Diluted [Abstract]
Weighted average common shares outstanding during the period - shares used for basic earnings per common share	10,015	9,931
Common shares issuable under share based payment plans which are potentially dilutive	70	70
Common shares used for diluted earnings per common share	10,085	10,001
Net income attributable to the Company	$ 1,560	$ 1,443
Earnings per common share:
Basic	$ 0.16	$ 0.15
Diluted	$ 0.15	$ 0.14