Condensed Consolidated Balance Sheets (Parentheticals) - $ / shares	Mar. 31, 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)	16,943,124	16,874,235
Common stock, shares outstanding (in shares)	15,859,515	16,201,634
Treasury stock, shares (in shares)	1,070,539	672,601