CONSOLIDATED BALANCE SHEETS (Parentheticals) - USD ($)
shares in Thousands, $ in Thousands
Dec. 31, 2016
Dec. 31, 2015
Accounts receivable, allowance for doubtful accounts (in dollars) $ 767 $ 618
Preferred stock, no par value (in dollars per share) $ 0 $ 0
Preferred stock, shares authorized 3,000 3,000
Preferred stock, shares issued 0 0
Treasury stock, a cost, shares 1,327 1,316
Class A common stock    
Common stock, no par value (in dollars per share) $ 0 $ 0
Common stock, shares authorized 30,000 30,000
Common stock, shares issued 20,935 20,652
Common stock, shares outstanding 19,608 19,177
Class B common stock    
Common stock, no par value (in dollars per share) $ 0 $ 0
Common stock, shares authorized 5,000 5,000
Common stock, shares issued 0 0