Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Allowance for doubtful accounts	$ 144	$ 175
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	2,000,000	2,000,000
Preferred stock, shares issued (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	60,000,000	60,000,000
Common stock, shares issued (in shares)	30,151,574	29,917,667
Common stock, shares outstanding (in shares)	24,947,500	24,800,796
Treasury stock, shares (in shares)	5,204,074	5,116,871