Condensed Consolidated Balance Sheets (Parentheticals) - $ / shares	Jun. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
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)	200,000,000	200,000,000
Common stock, shares issued (in shares)	18,008,577	17,129,680
Common stock, shares outstanding (in shares)	16,899,281	16,043,630
Treasury stock, shares (in shares)	1,109,296	1,086,050