Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Trade accounts receivable, allowance for doubtful accounts	$ 346	$ 317
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)	20,522,427	20,373,519
Common stock, shares outstanding (in shares)	16,089,832	15,959,984
Treasury stock, shares (in shares)	4,432,595	4,413,535