Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Allowances for accounts and notes receivable	$ 1,929	$ 1,632
Preferred stock, par value (USD per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	25,000,000	25,000,000
Preferred stock, shares outstanding	0	0
Common stock, par value (USD per share)	$ 0.01	$ 0.01
Common stock, Class A
Common stock, shares authorized	240,000,000	240,000,000
Common stock, shares issued	70,245,801	70,042,300
Common stock, shares outstanding	70,245,801	70,042,300
Voting common stock
Common stock, shares authorized	60,000,000	60,000,000
Common stock, shares issued	11,932,722	11,932,722
Common stock, shares outstanding	11,932,722	11,932,722