Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Common Class A [Member]
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	23,993,000	23,676,000
Common stock, shares outstanding (in shares)	23,993,000	23,676,000
Common Class B [Member]
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	25,000,000	25,000,000
Common stock, shares issued (in shares)	1,762,000	2,542,000
Common stock, shares outstanding (in shares)	1,762,000	2,542,000
Allowance for doubtful accounts	$ 3,729	$ 2,243
Accumulated depreciation	$ 145,033	$ 137,853
Preferred stock, par value (in dollars per share)	$ 0	$ 0
Preferred stock, shares authorized (in shares)	15,000,000	15,000,000
Preferred stock, shares outstanding (in shares)	0	0