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Statements Of Condensed Consolidated Financial Position (Parenthetical) (USD $)
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Dec. 31, 2014
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Dec. 31, 2013
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| Class of Stock [Line Items] | ||
| Preferred stock, par value | $ 0us-gaap_PreferredStockParOrStatedValuePerShare | $ 0us-gaap_PreferredStockParOrStatedValuePerShare |
| Cumulative Mandatory Convertible | 7.00%clf_CumulativeMandatoryConvertible | 7.00%clf_CumulativeMandatoryConvertible |
| Common shares, par value | $ 0.125us-gaap_CommonStockParOrStatedValuePerShare | $ 0.125us-gaap_CommonStockParOrStatedValuePerShare |
| Common shares, authorized (in shares) | 400,000,000us-gaap_CommonStockSharesAuthorized | 400,000,000us-gaap_CommonStockSharesAuthorized |
| Common shares, issued (in shares) | 159,546,224us-gaap_CommonStockSharesIssued | 159,546,224us-gaap_CommonStockSharesIssued |
| Common shares, outstanding | 153,246,754us-gaap_CommonStockSharesOutstanding | 153,126,291us-gaap_CommonStockSharesOutstanding |
| Common shares in treasury | 6,299,470us-gaap_TreasuryStockShares | 6,419,133us-gaap_TreasuryStockShares |
| Preferred Class A [Member] | ||
| Class of Stock [Line Items] | ||
| Preferred Stock, Liquidation Preference Per Share |
$ 1,000us-gaap_PreferredStockLiquidationPreference / us-gaap_StatementClassOfStockAxis = us-gaap_PreferredClassAMember |
$ 1,000us-gaap_PreferredStockLiquidationPreference / us-gaap_StatementClassOfStockAxis = us-gaap_PreferredClassAMember |
| Preferred stock, shares authorized (in shares) |
3,000,000us-gaap_PreferredStockSharesAuthorized / us-gaap_StatementClassOfStockAxis = us-gaap_PreferredClassAMember |
3,000,000us-gaap_PreferredStockSharesAuthorized / us-gaap_StatementClassOfStockAxis = us-gaap_PreferredClassAMember |
| Preferred Shares, Issued and Outstanding, Shares |
731,223clf_PreferredSharesIssuedAndOutstandingShares / us-gaap_StatementClassOfStockAxis = us-gaap_PreferredClassAMember |
731,250clf_PreferredSharesIssuedAndOutstandingShares / us-gaap_StatementClassOfStockAxis = us-gaap_PreferredClassAMember |
| Preferred Class B [Member] | ||
| Class of Stock [Line Items] | ||
| Preferred stock, shares authorized (in shares) |
4,000,000us-gaap_PreferredStockSharesAuthorized / us-gaap_StatementClassOfStockAxis = us-gaap_PreferredClassBMember |
4,000,000us-gaap_PreferredStockSharesAuthorized / us-gaap_StatementClassOfStockAxis = us-gaap_PreferredClassBMember |
| X | ||||||||||
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- Definition
Cumulative Mandatory Convertible No definition available.
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| X | ||||||||||
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- Definition
Preferred Shares, Issued and Outstanding, Shares No definition available.
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| X | ||||||||||
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- Details
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| X | ||||||||||
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- Definition
Face amount or stated value per share of common stock. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The maximum number of common shares permitted to be issued by an entity's charter and bylaws. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The per share liquidation preference (or restrictions) of nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) that has a preference in involuntary liquidation considerably in excess of the par or stated value of the shares. The liquidation preference is the difference between the preference in liquidation and the par or stated values of the share. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Details
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| X | ||||||||||
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- Details
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