Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Trade accounts receivable, allowance for doubtful accounts	$ 325	$ 346
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)	20,560,796	20,522,427
Common stock, shares outstanding (in shares)	16,127,082	16,089,832
Treasury stock, shares (in shares)	4,433,714	4,432,595