Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accounts receivable, allowance for doubtful accounts	$ 241	$ 666
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	1,000,000	1,000,000
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	25,000,000	25,000,000
Common stock, shares issued (in shares)	12,121,484	12,121,484
Common stock, shares outstanding (in shares)	6,599,309	6,302,936
Treasury stock, shares (in shares)	5,522,175	5,818,548
Series A Preferred Stock [Member]
Preferred stock, shares issued (in shares)	9,926	9,926
Preferred stock, shares outstanding (in shares)	9,926	9,926