Consolidated Balance Sheets (Parenthetical) $ in Thousands	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares
Statement of Financial Position [Abstract]
Allowances for account receivable | $	$ 1,523	$ 1,523
Class A Common Stock
Common stock, par value (in usd per share) | $ / shares	$ 1	$ 1
Common stock, shares outstanding (in shares) | shares	5,352,590	5,282,106
Class B Common Stock
Common stock, par value (in usd per share) | $ / shares	$ 1	$ 1
Common stock, shares outstanding (in shares) | shares	1,568,810	1,570,146
Common stock, convertible conversion ratio	1	1