Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $) In Thousands, except Share data	Jun. 30, 2011	Dec. 31, 2010
Current assets:
Allowances for accounts and notes receivable	$ 2,302	$ 2,789
Equity:
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	25,000,000	25,000,000
Preferred stock, shares outstanding	0	0
Common stock, Class A
Equity:
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	240,000,000	240,000,000
Common stock, shares issued	45,849,103	46,403,887
Common stock, shares outstanding	45,849,103	46,403,887
Common stock, Voting
Equity:
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	60,000,000	60,000,000
Common stock, shares issued	11,932,735	11,932,735
Common stock, shares outstanding	11,932,735	11,932,735