Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - $ / shares	Jun. 30, 2023	Dec. 31, 2022
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	70,107,739	69,306,497
Common stock, shares outstanding (in shares)	70,074,406	69,273,164
Treasury stock, shares (in shares)	33,333	33,333