Consolidated Balance Sheets (Parentheticals) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Common stock, par value per share (USD per share)	$ 0.01	$ 0.01
Common stock, shares authorized (shares)	40,000,000	40,000,000
Common stock, shares issued (shares)	25,022,312	25,134,223
Common stock, shares outstanding (shares)	17,993,124	17,969,636
Treasury stock, shares outstanding (shares)	7,029,188	7,164,587