Consolidated Balance Sheets (Parentheticals) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
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)	42,503,925	41,930,472
Treasury stock (in shares)	10,335	7,583,674
Common Class B [Member]
Common stock, authorized (in shares)	20,000,000	20,000,000
Common stock, outstanding (in shares)	12,470,308	12,360,729
Treasury stock (in shares)	73,437	7,959,511