Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Accounts and notes receivable, net of allowance for doubtful accounts	$ 6,582	$ 7,471
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	100,000,000us-gaap_PreferredStockSharesAuthorized	100,000,000us-gaap_PreferredStockSharesAuthorized
Preferred stock, shares issued	0us-gaap_PreferredStockSharesIssued	0us-gaap_PreferredStockSharesIssued
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	225,000,000us-gaap_CommonStockSharesAuthorized	225,000,000us-gaap_CommonStockSharesAuthorized
Common stock, shares issued	153,050,285us-gaap_CommonStockSharesIssued	152,821,011us-gaap_CommonStockSharesIssued
Cost of common stock held in treasury, shares	15,877,371us-gaap_TreasuryStockShares	15,922,729us-gaap_TreasuryStockShares
Common stock held in employee benefit and compensation trusts, shares	72,679	80,967

For an unclassified balance sheet, a valuation allowance for receivables due a company that are expected to be uncollectible.

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