Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]
Receivables, allowance for doubtful accounts	$ 0	$ 50
Preferred stock,par value	$ 0.01	$ 0.01
Preferred stock,shares authorized	10,000,000us-gaap_PreferredStockSharesAuthorized	10,000,000us-gaap_PreferredStockSharesAuthorized
Preferred stock,shares issued	0us-gaap_PreferredStockSharesIssued	0us-gaap_PreferredStockSharesIssued
Preferred stock,shares outstanding	0us-gaap_PreferredStockSharesOutstanding	0us-gaap_PreferredStockSharesOutstanding
Common stock,par value	$ 0.01	$ 0.01
Common stock,shares authorized	250,000,000us-gaap_CommonStockSharesAuthorized	250,000,000us-gaap_CommonStockSharesAuthorized
Common stock,shares issued	137,093,424us-gaap_CommonStockSharesIssued	137,081,056us-gaap_CommonStockSharesIssued
Treasury stock,shares	31,386,746us-gaap_TreasuryStockShares	30,515,721us-gaap_TreasuryStockShares

A valuation allowance for trade and other receivables due to an Entity within one year (or the normal operating cycle, whichever is longer) that are expected to be uncollectible.

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Face amount or stated value per share of common stock.

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer.

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Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased.

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Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

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