Consolidated Balance Sheets (Parentheticals) - $ / shares	Dec. 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)	120,000,000	120,000,000
Common stock, shares issued (in shares)	41,091,606	32,133,263
Common stock, shares outstanding (in shares)	41,091,532	32,133,189
Treasury stock, shares (in shares)	74	74