Consolidated Balance Sheets (Parentheticals) - $ / shares	Jun. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	40,000,000	40,000,000
Common stock, shares issued (in shares)	25,005,404	25,022,312
Common stock, shares outstanding (in shares)	17,802,953	17,993,124
Treasury stock, shares (in shares)	7,202,451	7,029,188