Consolidated Balance Sheets (Parenthetical) $ in Thousands	Dec. 31, 2019 USD ($) Vote $ / shares shares	Dec. 31, 2018 USD ($) Vote $ / shares shares
Accounts receivable, allowance | $	$ 59	$ 224
Treasury stock, shares	11,634,806	11,635,739
Class B Common Stock [Member]
Common Stock, votes per share | Vote	10	10
Common Stock, par value | $ / shares	$ 0.01	$ 0.01
Common Stock, shares authorized	14,000,000	14,000,000
Common Stock, shares issued	11,758,218	11,758,218
Common Stock, shares outstanding	11,758,218	11,758,218
Common Stock [Member]
Common Stock, votes per share | Vote	1	1
Common Stock, par value | $ / shares	$ 0.01	$ 0.01
Common Stock, shares authorized	62,000,000	62,000,000
Common Stock, shares issued	40,403,058	40,066,710
Common Stock, shares outstanding	28,768,252	28,430,971