Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - $ / shares	Jun. 30, 2023	Dec. 31, 2022
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized (in shares)	10,000,000	10,000,000
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, authorized (in shares)	200,000,000	200,000,000
Common stock, issued (in shares)	28,462,606	27,044,900
Common stock, outstanding (in shares)	26,362,870	25,097,963
Treasury stock, shares (in shares)	2,099,736	1,946,937