STOCK COMPENSATION PLANS STOCK COMPENSATION PLANS (Incentive Compensation and Other Benefit Plans for Employees and Directors) (Details)

v2.4.1.9

STOCK COMPENSATION PLANS STOCK COMPENSATION PLANS (Incentive Compensation and Other Benefit Plans for Employees and Directors) (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restricted Equity Grant Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Issued During Period Shares Director Stock Award	73,635clf_StockIssuedDuringPeriodSharesDirectorStockAward / us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis = clf_RestrictedEquityGrantSharesMember	31,506clf_StockIssuedDuringPeriodSharesDirectorStockAward / us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis = clf_RestrictedEquityGrantSharesMember	8,988clf_StockIssuedDuringPeriodSharesDirectorStockAward / us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis = clf_RestrictedEquityGrantSharesMember
Deferred Equity Grant Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Issued During Period Shares Director Stock Award	0clf_StockIssuedDuringPeriodSharesDirectorStockAward / us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis = clf_DeferredEquityGrantSharesMember	7,970clf_StockIssuedDuringPeriodSharesDirectorStockAward / us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis = clf_DeferredEquityGrantSharesMember	2,996clf_StockIssuedDuringPeriodSharesDirectorStockAward / us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis = clf_DeferredEquityGrantSharesMember
Unrestricted Equity Grant Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Issued During Period Shares Director Stock Award	0clf_StockIssuedDuringPeriodSharesDirectorStockAward / us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis = clf_UnrestrictedEquityGrantSharesMember	3,985clf_StockIssuedDuringPeriodSharesDirectorStockAward / us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis = clf_UnrestrictedEquityGrantSharesMember	1,498clf_StockIssuedDuringPeriodSharesDirectorStockAward / us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis = clf_UnrestrictedEquityGrantSharesMember