CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Statement Of Financial Position [Abstract]
Accumulated amortization on deferred charges	$ 38,796	$ 41,605
Common shares, par value	$ 0.10	$ 0.10
Common shares, shares authorized	600,000,000us-gaap_CommonStockSharesAuthorized	600,000,000us-gaap_CommonStockSharesAuthorized
Common shares, shares issued	360,711,232us-gaap_CommonStockSharesIssued	359,378,751us-gaap_CommonStockSharesIssued
Treasury at cost	957,068us-gaap_TreasuryStockShares	1,030,053us-gaap_TreasuryStockShares

For an unclassified balance sheet, the accumulated amortization, as of the reporting date, representing the periodic charge to earnings of deferred costs which are associated with debt obligations existing as of the end of the period.

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

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Face amount or stated value per share of common stock.

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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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Reference 1: 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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