Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) shares in Thousands, $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accounts receivable, allowance for doubtful accounts	$ 154	$ 213
Preferred stock, par value (in dollars per share)	$ 0.00015	$ 0.00015
Preferred stock, shares authorized (in shares)	5,000	5,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.00015	$ 0.00015
Common stock, shares authorized (in shares)	70,000	70,000
Common stock, shares issued (in shares)	42,182	41,797
Common stock, shares outstanding (in shares)	32,795	32,503
Treasury stock, shares (in shares)	9,387	9,294