Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]
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	87,253,657us-gaap_CommonStockSharesIssued	87,081,862us-gaap_CommonStockSharesIssued
Common stock, shares outstanding	86,030,811us-gaap_CommonStockSharesOutstanding	85,859,016us-gaap_CommonStockSharesOutstanding
Treasury stock, at cost	1,222,846us-gaap_TreasuryStockShares	1,222,846us-gaap_TreasuryStockShares

Face amount or stated value per share of common stock.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

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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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Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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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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