Interim Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - $ / shares	Mar. 31, 2019	Dec. 31, 2018
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	60,000,000	60,000,000
Common stock, shares issued (in shares)	23,595,160	23,595,160
Common stock, shares outstanding (in shares)	21,972,816	21,787,860
Treasury stock, shares (in shares)	1,622,344	1,807,300