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STOCK COMPENSATION PLANS (Assumptions Utilized To Estimate Fair Value For Performance Share Grants) (Details) (Performance Shares [Member], USD $) | 3 Months Ended
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Mar. 31, 2015
January 12, 2015 [Member] |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Grant Date Market Price | $ 7.70 clf_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDatePrice / us-gaap_AwardDateAxis = clf_January122015Member / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember
Average Expected Term (Years) | 2 years 11 months 20 days
Expected Volatility | 58.30%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate / us-gaap_AwardDateAxis = clf_January122015Member / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember
Risk-Free Interest Rate | 0.91%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / us-gaap_AwardDateAxis = clf_January122015Member / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember
Dividend Yield | 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / us-gaap_AwardDateAxis = clf_January122015Member / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember
Fair Value | $ 11.56 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / us-gaap_AwardDateAxis = clf_January122015Member / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember
Fair Value (Percent of Grant Date Market Price) | 150.13%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPriceOfferingDate / us-gaap_AwardDateAxis = clf_January122015Member / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember
February 9, 2015 [Member] |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Grant Date Market Price | $ 6.57 clf_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDatePrice / us-gaap_AwardDateAxis = clf_February92015Member / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember
Average Expected Term (Years) | 2 years 10 months 20 days
Expected Volatility | 58.30%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate / us-gaap_AwardDateAxis = clf_February92015Member / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember
Risk-Free Interest Rate | 0.87%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / us-gaap_AwardDateAxis = clf_February92015Member / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember
Dividend Yield | 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / us-gaap_AwardDateAxis = clf_February92015Member / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember
Fair Value | $ 9.86 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / us-gaap_AwardDateAxis = clf_February92015Member / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember
Fair Value (Percent of Grant Date Market Price) | 150.13%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPriceOfferingDate / us-gaap_AwardDateAxis = clf_February92015Member / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember

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- Definition Share Based Compensation Arrangement by Share Based Payment Award Grant Date Price + References No definition available. + Details
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- Definition Discount rate from fair value on offering date that participants pay for shares. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 14.D.2) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 14 -Section D -Subsection 2 + Details
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- Definition The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The risk-free interest rate assumption that is used in valuing an option on its own shares. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(iv) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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