Annual report pursuant to Section 13 and 15(d)

STOCK COMPENSATION PLANS (Assumptions Utilized To Estimate Fair Value For Performance Share Grants) (Details)

Betfred-casino review_OF FINANCIAL INSTRUMENTS v2.4.1.9
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3 Months Ended 12 Months Ended
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Fair Value       $ 16.67us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Performance Shares [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Grant Date Market Price $ 17.62clf_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDatePrice
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
$ 17.54clf_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDatePrice
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
$ 20.58clf_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDatePrice
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
$ 10.85clf_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDatePrice
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
betfred sportsbook reviewAverage Expected Term (Years) 2 years 5 months 2 years 7 months 11 days 2 years 10 months 21 days 3 years 1 month 14 days
Expected Volatility 51.30%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
54.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
54.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
52.90%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
Risk-Free Interest Rate 0.83%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
0.54%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
0.54%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
1.18%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
Dividend Yield 3.40%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
2.92%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
2.92%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
4.30%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
Fair Value $ 19.02us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
$ 18.93us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
$ 22.21us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
$ 10.61us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
Fair Value (Percent of Grant Date Market Price) 107.92%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPriceOfferingDate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
107.92%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPriceOfferingDate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
107.92%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPriceOfferingDate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
97.79%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPriceOfferingDate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember