Consolidated Balance Sheets (Parentheticals) - USD ($) shares in Thousands, $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Allowance for doubtful accounts	$ 89	$ 37
Preferred stock, par value (in dollars per share)	$ 0.005	$ 0.005
Preferred stock, shares authorized (in shares)	873	873
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.005	$ 0.005
Common stock, shares authorized (in shares)	50,000	50,000
Common stock, shares issued (in shares)	6,257	6,205
Common stock, shares outstanding (in shares)	5,589	5,537
Treasury stock, shares (in shares)	668	668