Consolidated Balance Sheets (Parentheticals) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized (in shares)	1,000,000	1,000,000
Preferred stock, outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common Class A [Member]
Common stock, authorized (in shares)	60,000,000	60,000,000
Common stock, outstanding (in shares)	31,345,116	30,007,088
Treasury stock (in shares)	934,171	934,171
Common Class B [Member]
Common stock, authorized (in shares)	20,000,000	20,000,000
Common stock, outstanding (in shares)	8,469,247	9,245,447
Treasury stock (in shares)	4,625,181	3,650,491