Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Trade accounts receivable, allowance for doubtful accounts	$ 311	$ 324
Preferred stock, par value (in dollars per share)	$ 0.10	$ 0.10
Preferred stock, shares authorized (in shares)	1,000,000	1,000,000
Preferred stock, shares issued (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.10	$ 0.10
Common stock, shares authorized (in shares)	40,000,000	40,000,000
Common stock, shares issued (in shares)	20,281,516	20,268,050
Common stock, shares outstanding (in shares)	15,879,284	15,866,868
Treasury stock, shares (in shares)	4,402,232	4,401,182