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Annual report pursuant to Section 13 and 15(d)

Statements of Consolidated Changes in Equity

v2.4.1.9
Statements of Consolidated Changes in Equity (USD $)
In Millions, except Share data, unless otherwise specified
Total
USD ($)
Depositary Shares [Member]
USD ($)
Common Stock [Member]
USD ($)
Capital in Excess of Par Value of Shares [Member]
USD ($)
Retained Earnings [Member]
USD ($)
Common Shares in Treasury [Member]
USD ($)
Accumulated Other Comprehensive Income (Loss) [Member]
USD ($)
Noncontrolling Interest [Member]
USD ($)
Depositary Shares [Member]
USD ($)
Depositary Shares [Member]
Capital in Excess of Par Value of Shares [Member]
USD ($)
Common Stock [Member]
Common Stock [Member]
Capital in Excess of Par Value of Shares [Member]
USD ($)
Balance, beginning of period at Dec. 31, 2011 $ 7,039.7us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest Ìý $ 18.5us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember 		$ 1,770.8us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AdditionalPaidInCapitalMember 		$ 4,424.3us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_RetainedEarningsMember 		$ (336.0)us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_TreasuryStockMember 		$ (92.6)us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedOtherComprehensiveIncomeMember 		$ 1,254.7us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember 		Ìý Ìý Ìý Ìý
Balance, beginning of period (in shares) at Dec. 31, 2011 Ìý Ìý 142,000,000us-gaap_CommonStockSharesOutstanding
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember 		Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract] Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
NET INCOME (LOSS) (1,126.6)us-gaap_ProfitLoss Ìý Ìý Ìý (899.4)us-gaap_ProfitLoss
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_RetainedEarningsMember 		Ìý Ìý (227.2)us-gaap_ProfitLoss
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember 		Ìý Ìý Ìý Ìý
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent 862.4us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent Ìý Ìý Ìý Ìý Ìý 37.0us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedOtherComprehensiveIncomeMember 		Ìý Ìý Ìý Ìý Ìý
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Ìý Ìý Ìý Ìý Ìý Ìý Ìý 7.6us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember 		Ìý Ìý Ìý Ìý
Other Comprehensive Income (Loss), Net of Tax 44.6us-gaap_OtherComprehensiveIncomeLossNetOfTax Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Pension and OPEB liability, net of tax 33.8us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Unrealized net loss on marketable securities, net of tax (0.5)us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Total comprehensive income (loss) (1,082.0)us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest Ìý Ìý Ìý Ìý Ìý Ìý (219.6)us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember 		Ìý Ìý Ìý Ìý
Purchase of subsidiary shares from noncontrolling interest (2.1)us-gaap_MinorityInterestDecreaseFromRedemptions Ìý Ìý Ìý Ìý Ìý Ìý (2.1)us-gaap_MinorityInterestDecreaseFromRedemptions
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember 		Ìý Ìý Ìý Ìý
Undistributed losses to noncontrolling interest to subsidiary 0.4clf_UndistributedEarningsLossesRelatedToNoncontrollingInterests Ìý Ìý Ìý Ìý Ìý Ìý 0.4clf_UndistributedEarningsLossesRelatedToNoncontrollingInterests
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember 		Ìý Ìý Ìý Ìý
Capital contribution by noncontrolling interest to subsidiary 104.4us-gaap_ProceedsFromMinorityShareholders Ìý Ìý 1.6us-gaap_ProceedsFromMinorityShareholders
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AdditionalPaidInCapitalMember 		Ìý Ìý Ìý 102.8us-gaap_ProceedsFromMinorityShareholders
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember 		Ìý Ìý Ìý Ìý
Stock Issued During Period, Value, Acquisitions (8.0)us-gaap_StockIssuedDuringPeriodValueAcquisitions Ìý Ìý Ìý Ìý Ìý Ìý (8.0)us-gaap_StockIssuedDuringPeriodValueAcquisitions
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember 		Ìý Ìý Ìý Ìý
Stock and other incentive plans (in shares) Ìý Ìý 500,000us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember 		Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Stock and other incentive plans 15.7us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation Ìý Ìý 2.3us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AdditionalPaidInCapitalMember 		Ìý 13.4us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_TreasuryStockMember 		Ìý Ìý Ìý Ìý Ìý Ìý
Common stock dividends ($0.60 per share) (307.2)us-gaap_DividendsCommonStock Ìý Ìý Ìý (307.2)us-gaap_DividendsCommonStock
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_RetainedEarningsMember 		Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Preferred stock dividends ($1.66 per depositary share) 0us-gaap_DividendsPreferredStock Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Balance, end of period at Dec. 31, 2012 5,760.9us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest Ìý 18.5us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember 		1,774.7us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AdditionalPaidInCapitalMember 		3,217.7us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_RetainedEarningsMember 		(322.6)us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_TreasuryStockMember 		(55.6)us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedOtherComprehensiveIncomeMember 		1,128.2us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember 		Ìý Ìý Ìý Ìý
Balance, end of period (in shares) at Dec. 31, 2012 Ìý Ìý 142,500,000us-gaap_CommonStockSharesOutstanding
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember 		Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract] Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
NET INCOME (LOSS) 361.8us-gaap_ProfitLoss Ìý Ìý Ìý 413.5us-gaap_ProfitLoss
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_RetainedEarningsMember 		Ìý Ìý (51.7)us-gaap_ProfitLoss
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember 		Ìý Ìý Ìý Ìý
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent (356.2)us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent Ìý Ìý Ìý Ìý Ìý (57.3)us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedOtherComprehensiveIncomeMember 		Ìý Ìý Ìý Ìý Ìý
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Ìý Ìý Ìý Ìý Ìý Ìý Ìý 30.5us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember 		Ìý Ìý Ìý Ìý
Other Comprehensive Income (Loss), Net of Tax (26.8)us-gaap_OtherComprehensiveIncomeLossNetOfTax Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Pension and OPEB liability, net of tax 208.3us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Unrealized net loss on marketable securities, net of tax 3.1us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Total comprehensive income (loss) 335.0us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest Ìý Ìý Ìý Ìý Ìý Ìý (21.2)us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember 		Ìý Ìý Ìý Ìý
Equity offering (in shares) Ìý 29,300,000us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_StatementEquityComponentsAxis
= clf_DepositarySharesMember 		10,400,000us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember 		Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Equity offering 285.3us-gaap_StockIssuedDuringPeriodValueNewIssues 731.3us-gaap_StockIssuedDuringPeriodValueNewIssues
/ us-gaap_StatementEquityComponentsAxis
= clf_DepositarySharesMember 		1.3us-gaap_StockIssuedDuringPeriodValueNewIssues
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember 		Ìý Ìý Ìý Ìý Ìý 709.4us-gaap_StockIssuedDuringPeriodValueNewIssues
/ us-gaap_StatementClassOfStockAxis
= clf_DepositarySharesMember 		(21.9)us-gaap_StockIssuedDuringPeriodValueNewIssues
/ us-gaap_StatementClassOfStockAxis
= clf_DepositarySharesMember
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AdditionalPaidInCapitalMember 		Ìý 284.0us-gaap_StockIssuedDuringPeriodValueNewIssues
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonStockMember
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AdditionalPaidInCapitalMember
Purchase of subsidiary shares from noncontrolling interest Ìý Ìý Ìý 295.4us-gaap_MinorityInterestDecreaseFromRedemptions
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AdditionalPaidInCapitalMember 		(82.7)us-gaap_MinorityInterestDecreaseFromRedemptions
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_RetainedEarningsMember 		Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Undistributed losses to noncontrolling interest to subsidiary 17.0clf_UndistributedEarningsLossesRelatedToNoncontrollingInterests Ìý Ìý Ìý Ìý Ìý Ìý 17.0clf_UndistributedEarningsLossesRelatedToNoncontrollingInterests
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember 		Ìý Ìý Ìý Ìý
Capital contribution by noncontrolling interest to subsidiary 5.2us-gaap_ProceedsFromMinorityShareholders Ìý Ìý 0.2us-gaap_ProceedsFromMinorityShareholders
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AdditionalPaidInCapitalMember 		(0.6)us-gaap_ProceedsFromMinorityShareholders
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_RetainedEarningsMember 		Ìý Ìý 5.6us-gaap_ProceedsFromMinorityShareholders
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember 		Ìý Ìý Ìý Ìý
Stock Issued During Period, Value, Acquisitions (102.1)us-gaap_StockIssuedDuringPeriodValueAcquisitions Ìý Ìý Ìý Ìý Ìý Ìý (314.8)us-gaap_StockIssuedDuringPeriodValueAcquisitions
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember 		Ìý Ìý Ìý Ìý
Stock and other incentive plans (in shares) Ìý Ìý 300,000us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember 		Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Stock and other incentive plans 14.2us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation Ìý Ìý (2.9)us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AdditionalPaidInCapitalMember 		Ìý 17.1us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_TreasuryStockMember 		Ìý Ìý Ìý Ìý Ìý Ìý
Common stock dividends ($0.60 per share) (91.9)us-gaap_DividendsCommonStock Ìý Ìý Ìý (91.9)us-gaap_DividendsCommonStock
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_RetainedEarningsMember 		Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Preferred stock dividends ($1.66 per depositary share) (48.7)us-gaap_DividendsPreferredStock Ìý Ìý Ìý (48.7)us-gaap_DividendsPreferredStock
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_RetainedEarningsMember 		Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Preferred Stock, Shares Outstanding Ìý 29,300,000us-gaap_PreferredStockSharesOutstanding
/ us-gaap_StatementEquityComponentsAxis
= clf_DepositarySharesMember 		Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Balance, end of period at Dec. 31, 2013 6,884.3us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest 731.3us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= clf_DepositarySharesMember 		19.8us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember 		2,329.5us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AdditionalPaidInCapitalMember 		3,407.3us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_RetainedEarningsMember 		(305.5)us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_TreasuryStockMember 		(112.9)us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedOtherComprehensiveIncomeMember 		814.8us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember 		Ìý Ìý Ìý Ìý
Balance, end of period (in shares) at Dec. 31, 2013 153,126,291us-gaap_CommonStockSharesOutstanding Ìý 153,200,000us-gaap_CommonStockSharesOutstanding
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember 		Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract] Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
NET INCOME (LOSS) (8,311.6)us-gaap_ProfitLoss Ìý Ìý Ìý (7,224.2)us-gaap_ProfitLoss
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_RetainedEarningsMember 		Ìý Ìý (1,087.4)us-gaap_ProfitLoss
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember 		Ìý Ìý Ìý Ìý
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent 7,357.1us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent Ìý Ìý Ìý Ìý Ìý (132.9)us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedOtherComprehensiveIncomeMember 		Ìý Ìý Ìý Ìý Ìý
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Ìý Ìý Ìý Ìý Ìý Ìý Ìý (4.8)us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember 		Ìý Ìý Ìý Ìý
Other Comprehensive Income (Loss), Net of Tax (137.7)us-gaap_OtherComprehensiveIncomeLossNetOfTax Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Pension and OPEB liability, net of tax (91.0)us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Unrealized net loss on marketable securities, net of tax (7.2)us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Total comprehensive income (loss) (8,449.3)us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest Ìý Ìý Ìý Ìý Ìý Ìý (1,092.2)us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember 		Ìý Ìý Ìý Ìý
Undistributed losses to noncontrolling interest to subsidiary (25.5)clf_UndistributedEarningsLossesRelatedToNoncontrollingInterests Ìý Ìý Ìý Ìý Ìý Ìý (25.5)clf_UndistributedEarningsLossesRelatedToNoncontrollingInterests
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember 		Ìý Ìý Ìý Ìý
Capital contribution by noncontrolling interest to subsidiary (0.1)us-gaap_ProceedsFromMinorityShareholders Ìý Ìý Ìý Ìý Ìý Ìý (0.1)us-gaap_ProceedsFromMinorityShareholders
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember 		Ìý Ìý Ìý Ìý
Stock and other incentive plans 0.1us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation Ìý Ìý (19.7)us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AdditionalPaidInCapitalMember 		Ìý 19.8us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_TreasuryStockMember 		Ìý Ìý Ìý Ìý Ìý Ìý
Common stock dividends ($0.60 per share) (92.5)us-gaap_DividendsCommonStock Ìý Ìý Ìý (92.5)us-gaap_DividendsCommonStock
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_RetainedEarningsMember 		Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Preferred stock dividends ($1.66 per depositary share) (51.2)us-gaap_DividendsPreferredStock Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Preferred Stock Dividends (51.3)clf_PreferredStockDividends Ìý Ìý Ìý (51.3)clf_PreferredStockDividends
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_RetainedEarningsMember 		Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Preferred Stock, Shares Outstanding Ìý 29,300,000us-gaap_PreferredStockSharesOutstanding
/ us-gaap_StatementEquityComponentsAxis
= clf_DepositarySharesMember 		Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Balance, end of period at Dec. 31, 2014 (1,734.3)us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest 731.3us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= clf_DepositarySharesMember 		19.8us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember 		2,309.8us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AdditionalPaidInCapitalMember 		(3,960.7)us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_RetainedEarningsMember 		(285.7)us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_TreasuryStockMember 		(245.8)us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedOtherComprehensiveIncomeMember 		(303.0)us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember 		Ìý Ìý Ìý Ìý
Balance, end of period (in shares) at Dec. 31, 2014 153,246,754us-gaap_CommonStockSharesOutstanding Ìý 153,200,000us-gaap_CommonStockSharesOutstanding
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember 		Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Balance, beginning of period at Sep. 30, 2014 Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract] Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Preferred stock dividends ($1.66 per depositary share) (12.8)us-gaap_DividendsPreferredStock Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Preferred Stock, Shares Outstanding Ìý 29,300,000us-gaap_PreferredStockSharesOutstanding
/ us-gaap_StatementEquityComponentsAxis
= clf_DepositarySharesMember 		Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Balance, end of period at Dec. 31, 2014 $ (1,734.3)us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest $ 731.3us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= clf_DepositarySharesMember 		$ 19.8us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember 		Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Balance, end of period (in shares) at Dec. 31, 2014 153,246,754us-gaap_CommonStockSharesOutstanding Ìý 153,200,000us-gaap_CommonStockSharesOutstanding
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember 		Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý