Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - $ / shares	Mar. 31, 2022	Dec. 31, 2021
Preferred stock, shares authorized (in shares)	20,000,000	20,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares outstanding (in shares)	65,906,465	65,614,597
Series B Convertible Preferred Stock [Member]
Preferred stock, shares authorized (in shares)	2,300,000	2,300,000
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares outstanding (in shares)	79,246	79,246