Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]
Accounts and notes receivable, net of allowance for doubtful accounts	$ 8,563	$ 7,573
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	100,000,000	100,000,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	225,000,000	225,000,000
Common stock, shares issued	152,450,629	150,869,239
Cost of common stock held in treasury, shares	16,223,318	16,418,710
Common stock held in employee benefit and compensation trusts, shares	89,703	76,095