Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Receivables, reserve	$ 4	$ 50
Intangible Assets, accumulated amortization	14,269	11,203
Property and Equipment, accumulated depreciation	91,603	$ 89,937
Right-of-Use Assets, accumulated amortization	$ 6,224
Treasury stock, shares (in shares)	8,294,433	8,702,074
Class A
Common stock, no par value (usd per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	20,000	20,000
Common stock, shares issued (in shares)	9,000	9,000
Common stock, shares outstanding (in shares)	9,000	9,000
Class B
Common stock, no par value (usd per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	900,000,000	900,000,000
Common stock, shares issued (in shares)	109,505,456	109,505,456