Condensed Consolidated Balance Sheets (Parentheticals) - $ / shares	Jun. 30, 2018	Dec. 31, 2017
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)	17,069,680	16,874,235
Common stock, shares outstanding (in shares)	15,997,361	16,201,634
Treasury stock, shares (in shares)	1,072,319	672,601