Condensed Consolidated Balance Sheets (Unaudited) (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Trade accounts receivable, allowance for doubtful accounts	$ 720	$ 691
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	17,792,244	17,689,928
Common stock, shares outstanding (in shares)	17,792,244	17,689,928