Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Receivables, reserve	$ 50	$ 60
Treasury stock, shares outstanding	8,702,074	8,405,003
Class A
Common stock, no par value (usd per share)	$ 0	$ 0
Common stock, shares authorized	20,000	20,000
Common stock, shares issued	9,000	9,000
Common stock, shares outstanding	9,000	9,000
Class B
Common stock, no par value (usd per share)	$ 0	$ 0
Common stock, shares authorized	900,000,000	900,000,000
Common stock, shares issued	109,505,456	109,505,456