$CLF
CLEVELAND-CLIFFS INC. Stock $clf

$clf Overview Financials Valuation SEC Filings Company Website

2019 Q4 Form 10-K Financial Statement

#000076406520000041 Filed on February 20, 2020

Income Statement

Concept	2019 Q4	2019 Q3	2019 Q2
Revenue	$534.1M	$555.6M	$743.2M
YoY Change	-23.29%	-25.1%	4.05%
Cost Of Revenue	$407.2M	$400.7M	$480.2M
YoY Change	-17.45%	-16.56%	11.73%
Gross Profit	$126.9M	$154.9M	$263.0M
YoY Change	-37.18%	-40.79%	-7.56%
Gross Profit Margin	23.76%	27.88%	35.39%
Selling, General & Admin	$37.20M	$25.50M	$29.40M
YoY Change	5.08%	-12.37%	12.21%
% of Gross Profit	29.31%	16.46%	11.18%
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$22.00M	$22.00M	$20.90M
YoY Change	7.84%	14.58%	-18.04%
% of Gross Profit	17.34%	14.2%	7.95%
Operating Expenses	$45.20M	$33.30M	$36.20M
YoY Change	14.14%	-7.76%	19.47%
Operating Profit	$81.70M	$121.6M	$226.8M
YoY Change	-49.69%	-46.08%	-10.78%
Interest Expense	-$24.70M	-$25.30M	-$26.10M
YoY Change	-5.0%	-14.24%	-16.61%
% of Operating Profit	-30.23%	-20.81%	-11.51%
Other Income/Expense, Net	$900.0K	-$25.00M	-$43.40M
YoY Change	-78.05%	-0.79%	63.16%
Pretax Income	$57.90M	$96.60M	$183.4M
YoY Change	-56.95%	-51.77%	-19.42%
Income Tax	-$5.500M	$4.800M	$22.00M
% Of Pretax Income	-9.5%	4.97%	12.0%
Net Earnings	$63.20M	$90.90M	$160.8M
YoY Change	-89.63%	-79.24%	-2.6%
Net Earnings / Revenue	11.83%	16.36%	21.64%
Basic Earnings Per Share	$0.23	$0.34	$0.59
Diluted Earnings Per Share	$0.23	$0.33	$0.57
COMMON SHARES
Basic Shares Outstanding	270.1M shares	270.0M shares	275.8M shares
Diluted Shares Outstanding		276.6M shares	285.5M shares

Balance Sheet

Concept	2019 Q4	2019 Q3	2019 Q2
SHORT-TERM ASSETS
Cash & Short-Term Investments	$353.0M	$399.0M	$377.0M
YoY Change	-57.11%	-55.52%	-53.05%
Cash & Equivalents	$353.0M	$399.3M	$377.2M
Short-Term Investments
Other Short-Term Assets	$75.00M	$40.70M	$42.30M
YoY Change	88.44%	116.49%	57.84%
Inventory	$317.0M	$328.0M	$219.0M
Prepaid Expenses
Receivables	$94.00M	$164.9M	$193.1M
Other Receivables	$59.00M	$59.00M	$59.00M
Total Short-Term Assets	$898.0M	$1.065B	$1.119B
YoY Change	-39.31%	-35.5%	-27.64%
LONG-TERM ASSETS
Property, Plant & Equipment	$1.929B	$1.770B	$1.597B
YoY Change	50.0%	54.6%	47.72%
Goodwill	$2.000M
YoY Change
Intangibles	$48.10M
YoY Change
Long-Term Investments
YoY Change
Other Assets	$215.0M	$114.9M	$118.3M
YoY Change	20.85%	-5.35%	0.51%
Total Long-Term Assets	$2.606B	$2.427B	$2.274B
YoY Change	27.12%	64.58%	51.12%
TOTAL ASSETS
Total Short-Term Assets	$898.0M	$1.065B	$1.119B
Total Long-Term Assets	$2.606B	$2.427B	$2.274B
Total Assets	$3.504B	$3.491B	$3.393B
YoY Change	-0.73%	11.72%	11.2%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$193.0M	$212.8M	$188.1M
YoY Change	3.32%	51.14%	58.07%
Accrued Expenses	$126.3M	$91.00M	$90.00M
YoY Change	-20.52%	-4.31%	5.76%
Deferred Revenue			$15.50M
YoY Change
Short-Term Debt	$0.00	$0.00	$0.00
YoY Change
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$409.0M	$458.5M	$437.4M
YoY Change	-12.64%	20.44%	-7.9%
LONG-TERM LIABILITIES
Long-Term Debt	$2.114B	$2.109B	$2.105B
YoY Change	1.01%	-8.3%	-8.38%
Other Long-Term Liabilities	$311.0M	$151.4M	$149.7M
YoY Change	151.62%	24.3%	-5.43%
Total Long-Term Liabilities	$2.425B	$2.261B	$2.254B
YoY Change	9.41%	-6.66%	-8.19%
TOTAL LIABILITIES
Total Short-Term Liabilities	$409.0M	$458.5M	$437.4M
Total Long-Term Liabilities	$2.425B	$2.261B	$2.254B
Total Liabilities	$3.146B	$3.131B	$3.108B
YoY Change	1.31%	-2.49%	-7.45%
SHAREHOLDERS EQUITY
Retained Earnings	-$2.842B	-$2.889B	-$2.953B
YoY Change	-7.13%	-20.95%	-27.85%
Common Stock
YoY Change
Preferred Stock
YoY Change
Treasury Stock (at cost)	$391.0M	$390.9M	$391.3M
YoY Change	110.1%	181.02%	165.29%
Treasury Stock Shares	31.80M shares	31.81M shares	3.879M shares
Shareholders Equity	$358.0M	$359.9M	$285.6M
YoY Change
Total Liabilities & Shareholders Equity	$3.504B	$3.491B	$3.393B
YoY Change	-0.73%	11.72%	11.2%

Cashflow Statement

Concept	2019 Q4	2019 Q3	2019 Q2
OPERATING ACTIVITIES
Net Income	$63.20M	$90.90M	$160.8M
YoY Change	-89.63%	-79.24%	-2.6%
Depreciation, Depletion And Amortization	$22.00M	$22.00M	$20.90M
YoY Change	7.84%	14.58%	-18.04%
Cash From Operating Activities	$175.4M	$238.2M	$263.9M
YoY Change	-40.14%	-5.4%	181.94%
INVESTING ACTIVITIES
Capital Expenditures	-$191.1M	-$153.5M	-$161.7M
YoY Change	96.6%	121.5%	444.44%
Acquisitions
YoY Change
Other Investing Activities	-$3.800M	-$3.600M	-$5.100M
YoY Change	72.73%	-21.74%	-492.31%
Cash From Investing Activities	-$194.9M	-$157.1M	-$166.8M
YoY Change	96.08%	112.58%	487.32%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	-27.20M	-59.00M	-150.1M
YoY Change	-89.83%	-28.05%	702.67%
NET CHANGE
Cash From Operating Activities	175.4M	238.2M	263.9M
Cash From Investing Activities	-194.9M	-157.1M	-166.8M
Cash From Financing Activities	-27.20M	-59.00M	-150.1M
Net Change In Cash	-46.70M	22.10M	-53.00M
YoY Change	-36.81%	-76.96%	-213.98%
FREE CASH FLOW
Cash From Operating Activities	$175.4M	$238.2M	$263.9M
Capital Expenditures	-$191.1M	-$153.5M	-$161.7M
Free Cash Flow	$366.5M	$391.7M	$425.6M
YoY Change	-6.07%	21.99%	245.17%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
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CY2019	clf	Debtredemptionpremiumspaid Debtredemptionpremiumspaid	5300000	USD
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CY2019	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2019	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2019
CY2019	dei	Entity Central Index Key EntityCentralIndexKey	0000764065
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CY2019	us-gaap	Capital Expenditure Discontinued Operations CapitalExpenditureDiscontinuedOperations	0	USD
CY2017	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0
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CY2018Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	600000000	shares
CY2019Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	600000000	shares
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CY2019Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	270084005	shares
CY2019Q4	us-gaap	Defined Benefit Plan Funded Percentage DefinedBenefitPlanFundedPercentage	0.7
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CY2019	dei	Document Type DocumentType	10-K
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CY2019	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	34-1464672
CY2019	dei	Entity Address Address Line1 EntityAddressAddressLine1	200 Public Square,
CY2019	dei	Entity File Number EntityFileNumber	1-8944
CY2019	dei	Entity Registrant Name EntityRegistrantName	CLEVELAND-CLIFFS INC.
CY2019	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	OH
CY2019	dei	Document Transition Report DocumentTransitionReport	false
CY2019	dei	Entity Address City Or Town EntityAddressCityOrTown	Cleveland,
CY2019	dei	Entity Address State Or Province EntityAddressStateOrProvince	OH
CY2019	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	44114-2315
CY2019	dei	City Area Code CityAreaCode	216
CY2019	dei	Local Phone Number LocalPhoneNumber	694-5700
CY2019	dei	Security12b Title Security12bTitle	Common Shares, par value $0.125 per share
CY2019	dei	Trading Symbol TradingSymbol	CLF
CY2019	dei	Security Exchange Name SecurityExchangeName	NYSE
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CY2019	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	1.07
CY2018	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	3.50
CY2017	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	1.27
CY2019	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	-0.01
CY2018	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	0.30
CY2017	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	0.01
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.06
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.80
CY2017	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.28
CY2019	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	1.04
CY2018	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	3.42
CY2017	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	1.25
CY2019	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	-0.01
CY2018	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	0.29
CY2017	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	0.01
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.03
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.71
CY2017	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.26
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	276761000	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	297176000	shares
CY2017	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	288435000	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	284480000	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	304141000	shares
CY2017	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	292961000	shares
CY2019	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	292800000	USD
CY2018	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	1128100000	USD
CY2017	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	367000000.0	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	34600000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	17200000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-11500000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	0	USD
CY2018	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	-225400000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-244900000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Net Of Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax	-2300000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Net Of Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax	-500000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-34900000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-2900000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	0	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	0	USD
CY2017	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	1100000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	257900000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	883200000	USD
CY2017	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	363000000.0	USD
CY2019	us-gaap	Profit Loss ProfitLoss	292800000	USD
CY2018	us-gaap	Profit Loss ProfitLoss	1128100000	USD
CY2017	us-gaap	Profit Loss ProfitLoss	363100000	USD
CY2019	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	85100000	USD
CY2018	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	89000000.0	USD
CY2017	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	87700000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	16800000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-460500000	USD
CY2017	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	0	USD
CY2019	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-18200000	USD
CY2018	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-6800000	USD
CY2017	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-165400000	USD
CY2019	us-gaap	Unrealized Gain Loss On Derivatives And Commodity Contracts UnrealizedGainLossOnDerivativesAndCommodityContracts	-46800000	USD
CY2018	us-gaap	Unrealized Gain Loss On Derivatives And Commodity Contracts UnrealizedGainLossOnDerivativesAndCommodityContracts	110200000	USD
CY2017	us-gaap	Unrealized Gain Loss On Derivatives And Commodity Contracts UnrealizedGainLossOnDerivativesAndCommodityContracts	4100000	USD
CY2019	us-gaap	Foreign Currency Transaction Gain Loss Realized ForeignCurrencyTransactionGainLossRealized	0	USD
CY2018	us-gaap	Foreign Currency Transaction Gain Loss Realized ForeignCurrencyTransactionGainLossRealized	228100000	USD
CY2017	us-gaap	Foreign Currency Transaction Gain Loss Realized ForeignCurrencyTransactionGainLossRealized	0	USD
CY2019	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-65400000	USD
CY2018	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-20700000	USD
CY2017	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-45500000	USD
CY2019	us-gaap	Increase Decrease In Accounts Receivable And Other Operating Assets IncreaseDecreaseInAccountsReceivableAndOtherOperatingAssets	-254500000	USD
CY2018	us-gaap	Increase Decrease In Accounts Receivable And Other Operating Assets IncreaseDecreaseInAccountsReceivableAndOtherOperatingAssets	-51700000	USD
CY2017	us-gaap	Increase Decrease In Accounts Receivable And Other Operating Assets IncreaseDecreaseInAccountsReceivableAndOtherOperatingAssets	246300000	USD
CY2019	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	136300000	USD
CY2018	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	-43500000	USD
CY2017	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	4200000	USD
CY2019	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	-80800000	USD
CY2018	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	-62500000	USD
CY2017	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	-69000000.0	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	562500000	USD
CY2018	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	478500000	USD
CY2017	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	338100000	USD
CY2019	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	639000000.0	USD
CY2018	clf	Paymentsfor Deposits On Property Plantand Equipment PaymentsforDepositsOnPropertyPlantandEquipment	87500000	USD
CY2017	clf	Paymentsfor Deposits On Property Plantand Equipment PaymentsforDepositsOnPropertyPlantandEquipment	16800000	USD
CY2019	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-11600000	USD
CY2018	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	208600000	USD
CY2017	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	134900000	USD
CY2019	clf	Paymentsfor Deposits On Property Plantand Equipment PaymentsforDepositsOnPropertyPlantandEquipment	17000000.0	USD
CY2017	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	4300000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-644400000	USD
CY2018	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-273100000	USD
CY2018	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-23000000.0	USD
CY2017	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-156000000.0	USD
CY2019	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	252900000	USD
CY2018	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	47500000	USD
CY2017	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	0	USD
CY2019	us-gaap	Payments Of Dividends PaymentsOfDividends	72100000	USD
CY2018	us-gaap	Payments Of Dividends PaymentsOfDividends	0	USD
CY2017	us-gaap	Payments Of Dividends PaymentsOfDividends	0	USD
CY2019	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	0	USD
CY2018	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	0	USD
CY2017	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	661300000	USD
CY2019	us-gaap	Proceeds From Issuance Of Senior Long Term Debt ProceedsFromIssuanceOfSeniorLongTermDebt	720900000	USD
CY2018	us-gaap	Proceeds From Issuance Of Senior Long Term Debt ProceedsFromIssuanceOfSeniorLongTermDebt	0	USD
CY2017	us-gaap	Proceeds From Issuance Of Senior Long Term Debt ProceedsFromIssuanceOfSeniorLongTermDebt	1771500000	USD
CY2019	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	6800000	USD
CY2018	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	1500000	USD
CY2017	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	28600000	USD
CY2019	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	729300000	USD
CY2018	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	234500000	USD
CY2017	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	1720700000	USD
CY2019	us-gaap	Payments For Repurchase Of Redeemable Noncontrolling Interest PaymentsForRepurchaseOfRedeemableNoncontrollingInterest	0	USD
CY2018	us-gaap	Payments For Repurchase Of Redeemable Noncontrolling Interest PaymentsForRepurchaseOfRedeemableNoncontrollingInterest	0	USD
CY2017	us-gaap	Payments For Repurchase Of Redeemable Noncontrolling Interest PaymentsForRepurchaseOfRedeemableNoncontrollingInterest	105000000.0	USD
CY2019	us-gaap	Payments Of Distributions To Affiliates PaymentsOfDistributionsToAffiliates	44200000	USD
CY2018	us-gaap	Payments Of Distributions To Affiliates PaymentsOfDistributionsToAffiliates	44200000	USD
CY2017	us-gaap	Payments Of Distributions To Affiliates PaymentsOfDistributionsToAffiliates	52900000	USD
CY2019	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-9700000	USD
CY2018	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-47500000	USD
CY2017	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-26700000	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-394100000	USD
CY2018	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-375200000	USD
CY2017	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	498900000	USD
CY2019	us-gaap	Effect Of Exchange Rate On Cash And Cash Equivalents EffectOfExchangeRateOnCashAndCashEquivalents	0	USD
CY2018	us-gaap	Effect Of Exchange Rate On Cash And Cash Equivalents EffectOfExchangeRateOnCashAndCashEquivalents	-2300000	USD
CY2017	us-gaap	Effect Of Exchange Rate On Cash And Cash Equivalents EffectOfExchangeRateOnCashAndCashEquivalents	3300000	USD
CY2019	clf	Increase Decreasein Cashand Cash Equivalents Including Cash Classified Within Other Current Assets Relatedto Discontinued Operations IncreaseDecreaseinCashandCashEquivalentsIncludingCashClassifiedWithinOtherCurrentAssetsRelatedtoDiscontinuedOperations	-476000000.0	USD
CY2018	clf	Increase Decreasein Cashand Cash Equivalents Including Cash Classified Within Other Current Assets Relatedto Discontinued Operations IncreaseDecreaseinCashandCashEquivalentsIncludingCashClassifiedWithinOtherCurrentAssetsRelatedtoDiscontinuedOperations	-172100000	USD
CY2017	clf	Increase Decreasein Cashand Cash Equivalents Including Cash Classified Within Other Current Assets Relatedto Discontinued Operations IncreaseDecreaseinCashandCashEquivalentsIncludingCashClassifiedWithinOtherCurrentAssetsRelatedtoDiscontinuedOperations	684300000	USD
CY2019	us-gaap	Net Cash Provided By Used In Discontinued Operations NetCashProvidedByUsedInDiscontinuedOperations	5400000	USD
CY2018	us-gaap	Net Cash Provided By Used In Discontinued Operations NetCashProvidedByUsedInDiscontinuedOperations	17000000.0	USD
CY2017	us-gaap	Net Cash Provided By Used In Discontinued Operations NetCashProvidedByUsedInDiscontinuedOperations	-18800000	USD
CY2019	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	-470600000	USD
CY2018	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	-155100000	USD
CY2017	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	665500000	USD
CY2018Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	823200000	USD
CY2017Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	978300000	USD
CY2016Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	312800000	USD
CY2019Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	352600000	USD
CY2018Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	823200000	USD
CY2017Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	978300000	USD
CY2016Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	-1330500000	USD
CY2017	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	360200000	USD
CY2017	us-gaap	Adjustments To Additional Paid In Capital Equity Component Of Convertible Debt AdjustmentsToAdditionalPaidInCapitalEquityComponentOfConvertibleDebt	83400000	USD
CY2017	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	661300000	USD
CY2017	clf	Undistributed Earnings Losses Related To Noncontrolling Interests UndistributedEarningsLossesRelatedToNoncontrollingInterests	-105000000.0	USD
CY2017	us-gaap	Minority Interest Decrease From Distributions To Noncontrolling Interest Holders MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders	128800000	USD
CY2017	clf	Capitalcontributionsbynoncontrollinginteresttosubsidiary Capitalcontributionsbynoncontrollinginteresttosubsidiary	1800000	USD
CY2017	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	13500000	USD
CY2017Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	-444100000	USD
CY2018	us-gaap	New Accounting Pronouncement Or Change In Accounting Principle Effect Of Adoption Quantification NewAccountingPronouncementOrChangeInAccountingPrincipleEffectOfAdoptionQuantification	34000000.0	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	883200000	USD
CY2018	clf	Capitalcontributionsbynoncontrollinginteresttosubsidiary Capitalcontributionsbynoncontrollinginteresttosubsidiary	-200000	USD
CY2018	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	13800000	USD
CY2018	us-gaap	Stock Repurchased During Period Value StockRepurchasedDuringPeriodValue	47500000	USD
CY2018	us-gaap	Dividends Common Stock DividendsCommonStock	15000000.0	USD
CY2018Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	424200000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	257900000	USD
CY2019	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	3700000	USD
CY2019	us-gaap	Stock Repurchased During Period Value StockRepurchasedDuringPeriodValue	252900000	USD
CY2019	us-gaap	Dividends Common Stock DividendsCommonStock	75000000.0	USD
CY2019Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	357900000	USD
CY2019	us-gaap	Nature Of Operations NatureOfOperations	<div style="line-height:120%;padding-bottom:12px;text-align:justify;font-size:10pt;"><span style="font-family:Arial;font-size:10pt;font-weight:bold;">Nature of Existing Business</span></div><div style="line-height:120%;padding-bottom:12px;text-align:justify;text-indent:48px;font-size:10pt;"><span style="font-family:Arial;font-size:10pt;"/><span style="font-family:Arial;font-size:10pt;">Founded in 1847, Cleveland-Cliffs Inc. is the largest and oldest independent iron ore mining company in the United States. We are a major supplier of iron ore pellets to the North American steel industry from our mines and pellet plants located in Michigan and Minnesota. In 2020, we expect to be the sole producer of HBI in the Great Lakes region with the startup of our first production plant in Toledo, Ohio.</span><span style="font-family:Arial;font-size:10pt;"> </span></div><div style="line-height:120%;padding-bottom:12px;text-align:justify;text-indent:48px;font-size:10pt;"><span style="font-family:Arial;font-size:10pt;">Our Company’s continuing operations are organized and managed in </span><span style="font-family:Arial;font-size:10pt;"><span>two</span></span><span style="font-family:Arial;font-size:10pt;"> operating segments according to our differentiated products. Our Mining and Pelletizing segment is a major supplier of iron ore pellets to the North American steel industry from our mines and pellet plants located in Michigan and Minnesota. Our Metallics segment includes our HBI production plant in Toledo, Ohio, which is currently under construction and expected to be completed during the first half of 2020. During the second quarter of 2019, Northshore mine began supplying DR-grade pellets to our Metallics segment, which will be used as feedstock for the HBI production plant when we begin production in 2020. </span></div><div style="line-height:120%;padding-bottom:12px;text-align:justify;text-indent:48px;font-size:10pt;"><span style="font-family:Arial;font-size:10pt;">Unless otherwise noted, discussion of our business and results of operations in this Annual Report on Form 10-K refers to our continuing operations on a stand-alone basis without giving effect to the Merger.</span></div>
CY2019	us-gaap	Number Of Reporting Units NumberOfReportingUnits	2	unit
CY2019	us-gaap	Use Of Estimates UseOfEstimates	<div style="line-height:120%;padding-bottom:12px;text-align:justify;text-indent:48px;font-size:10pt;"><span style="font-family:Arial;font-size:10pt;font-style:italic;font-weight:bold;">Use of Estimates</span></div><div style="line-height:120%;padding-bottom:12px;text-align:justify;text-indent:48px;font-size:10pt;"><span style="font-family:Arial;font-size:10pt;">The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. The more significant areas requiring the use of management estimates and assumptions relate to mineral reserves; future realizable cash flow; environmental, reclamation and closure obligations; valuation of long-lived assets, inventory, tax assets and post-employment, post-retirement and other employee benefit liabilities; reserves for contingencies and litigation; and the fair value of derivative instruments. Actual results could differ from estimates. Management reviews its estimates on an ongoing basis. Changes in facts and circumstances may alter such estimates and affect the results of operations and financial position in future periods.</span></div>
CY2019	us-gaap	Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet	7500000	USD
CY2018	us-gaap	Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet	422600000	USD
CY2018	us-gaap	Foreign Currency Transaction Gain Loss Realized ForeignCurrencyTransactionGainLossRealized	228100000	USD
CY2019	us-gaap	Revenues Revenues	1989900000	USD
CY2018	us-gaap	Revenues Revenues	2332400000	USD
CY2017	us-gaap	Revenues Revenues	1866000000.0	USD
CY2019Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	0	USD
CY2019Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	0	USD
CY2019	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	38500000	USD
CY2018	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	51300000	USD
CY2019Q4	us-gaap	Employee Related Liabilities Current EmployeeRelatedLiabilitiesCurrent	61700000	USD
CY2018Q4	us-gaap	Employee Related Liabilities Current EmployeeRelatedLiabilitiesCurrent	74000000.0	USD
CY2019Q4	us-gaap	Interest Payable Current InterestPayableCurrent	29000000.0	USD
CY2018Q4	us-gaap	Interest Payable Current InterestPayableCurrent	38400000	USD
CY2019Q4	us-gaap	Dividends Payable Current DividendsPayableCurrent	17800000	USD
CY2018Q4	us-gaap	Dividends Payable Current DividendsPayableCurrent	15000000.0	USD
CY2019Q4	us-gaap	Accrued Royalties Current AccruedRoyaltiesCurrent	8400000	USD
CY2018Q4	us-gaap	Accrued Royalties Current AccruedRoyaltiesCurrent	17300000	USD
CY2019Q4	us-gaap	Other Accrued Liabilities Current OtherAccruedLiabilitiesCurrent	9400000	USD
CY2018Q4	us-gaap	Other Accrued Liabilities Current OtherAccruedLiabilitiesCurrent	14200000	USD
CY2019Q4	us-gaap	Accrued Liabilities Current AccruedLiabilitiesCurrent	126300000	USD
CY2018Q4	us-gaap	Accrued Liabilities Current AccruedLiabilitiesCurrent	158900000	USD
CY2019	clf	Property Plantand Equipment Additions Including Discontinued Operations PropertyPlantandEquipmentAdditionsIncludingDiscontinuedOperations	689800000	USD
CY2018	clf	Property Plantand Equipment Additions Including Discontinued Operations PropertyPlantandEquipmentAdditionsIncludingDiscontinuedOperations	394800000	USD
CY2017	clf	Property Plantand Equipment Additions Including Discontinued Operations PropertyPlantandEquipmentAdditionsIncludingDiscontinuedOperations	156000000.0	USD
CY2019	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	-15300000	USD
CY2018	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	-93600000	USD
CY2017	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	2200000	USD
CY2019	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	29300000	USD
CY2018	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	7600000	USD
CY2017	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	6500000	USD
CY2019	clf	Governmentgrantrebate Governmentgrantrebate	-10800000	USD
CY2018	clf	Governmentgrantrebate Governmentgrantrebate	-2500000	USD
CY2017	clf	Governmentgrantrebate Governmentgrantrebate	0	USD
CY2019	clf	Payments To Acquire Property Plant And Equipment Net PaymentsToAcquirePropertyPlantAndEquipmentNet	-656000000.0	USD
CY2018	clf	Payments To Acquire Property Plant And Equipment Net PaymentsToAcquirePropertyPlantAndEquipmentNet	-296100000	USD
CY2017	clf	Payments To Acquire Property Plant And Equipment Net PaymentsToAcquirePropertyPlantAndEquipmentNet	-151700000	USD
CY2019	us-gaap	Income Taxes Paid IncomeTaxesPaid	200000	USD
CY2018	us-gaap	Income Taxes Paid IncomeTaxesPaid	2900000	USD
CY2017	us-gaap	Income Taxes Paid IncomeTaxesPaid	1700000	USD
CY2019	us-gaap	Proceeds From Income Tax Refunds ProceedsFromIncomeTaxRefunds	117900000	USD
CY2018	us-gaap	Proceeds From Income Tax Refunds ProceedsFromIncomeTaxRefunds	11300000	USD
CY2017	us-gaap	Proceeds From Income Tax Refunds ProceedsFromIncomeTaxRefunds	7800000	USD
CY2019	us-gaap	Interest Paid Net InterestPaidNet	97600000	USD
CY2018	us-gaap	Interest Paid Net InterestPaidNet	105700000	USD
CY2017	us-gaap	Interest Paid Net InterestPaidNet	139000000.0	USD
CY2019Q4	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.06
CY2019Q4	us-gaap	Dividends Payable Current And Noncurrent DividendsPayableCurrentAndNoncurrent	16200000	USD
CY2019	us-gaap	Number Of Reporting Units NumberOfReportingUnits	2	unit
CY2019	us-gaap	Revenues Revenues	1989900000	USD
CY2019	us-gaap	Gross Profit GrossProfit	575700000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	292800000	USD
CY2018	us-gaap	Profit Loss ProfitLoss	1128100000	USD
CY2017	us-gaap	Profit Loss ProfitLoss	363100000	USD
CY2019	clf	Ebitda EBITDA	497100000	USD
CY2018	clf	Ebitda EBITDA	878100000	USD
CY2017	clf	Ebitda EBITDA	330400000	USD
CY2019	clf	Adjusted Ebitda AdjustedEBITDA	524800000	USD
CY2018	clf	Adjusted Ebitda AdjustedEBITDA	766300000	USD
CY2017	clf	Adjusted Ebitda AdjustedEBITDA	459900000	USD
CY2019	clf	Ebitda EBITDA	497100000	USD
CY2018	clf	Ebitda EBITDA	878100000	USD
CY2017	clf	Ebitda EBITDA	330400000	USD
CY2019	clf	Adjusted Ebitda AdjustedEBITDA	524800000	USD
CY2018	clf	Adjusted Ebitda AdjustedEBITDA	766300000	USD
CY2017	clf	Adjusted Ebitda AdjustedEBITDA	459900000	USD
CY2019	clf	Depreciation Depletionand Amortizationexcluding Depreciation Amortizationand Depletionexpensefor Discontinued Operations DepreciationDepletionandAmortizationexcludingDepreciationAmortizationandDepletionexpenseforDiscontinuedOperations	85100000	USD
CY2018	clf	Depreciation Depletionand Amortizationexcluding Depreciation Amortizationand Depletionexpensefor Discontinued Operations DepreciationDepletionandAmortizationexcludingDepreciationAmortizationandDepletionexpenseforDiscontinuedOperations	73800000	USD
CY2017	clf	Depreciation Depletionand Amortizationexcluding Depreciation Amortizationand Depletionexpensefor Discontinued Operations DepreciationDepletionandAmortizationexcludingDepreciationAmortizationandDepletionexpenseforDiscontinuedOperations	73400000	USD
CY2019	us-gaap	Property Plant And Equipment Additions PropertyPlantAndEquipmentAdditions	689800000	USD
CY2018	us-gaap	Property Plant And Equipment Additions PropertyPlantAndEquipmentAdditions	394700000	USD
CY2017	us-gaap	Property Plant And Equipment Additions PropertyPlantAndEquipmentAdditions	153200000	USD
CY2019Q4	us-gaap	Assets Assets	3503800000	USD
CY2018Q4	us-gaap	Assets Assets	3529600000	USD
CY2017Q4	us-gaap	Assets Assets	2953400000	USD
CY2019	us-gaap	Revenues Revenues	1989900000	USD
CY2018	us-gaap	Revenues Revenues	2332400000	USD
CY2017	us-gaap	Revenues Revenues	1866000000.0	USD
CY2019Q4	us-gaap	Inventory Finished Goods Net Of Reserves InventoryFinishedGoodsNetOfReserves	114100000	USD
CY2018Q4	us-gaap	Inventory Finished Goods Net Of Reserves InventoryFinishedGoodsNetOfReserves	77800000	USD
CY2019Q4	us-gaap	Inventory Work In Process Net Of Reserves InventoryWorkInProcessNetOfReserves	68700000	USD
CY2018Q4	us-gaap	Inventory Work In Process Net Of Reserves InventoryWorkInProcessNetOfReserves	10100000	USD
CY2019Q4	us-gaap	Inventory Finished Goods And Work In Process Net Of Reserves InventoryFinishedGoodsAndWorkInProcessNetOfReserves	182800000	USD
CY2018Q4	us-gaap	Inventory Finished Goods And Work In Process Net Of Reserves InventoryFinishedGoodsAndWorkInProcessNetOfReserves	87900000	USD
CY2019Q4	us-gaap	Inventory Supplies Net Of Reserves InventorySuppliesNetOfReserves	134600000	USD
CY2018Q4	us-gaap	Inventory Supplies Net Of Reserves InventorySuppliesNetOfReserves	93200000	USD
CY2019Q4	us-gaap	Inventory Net InventoryNet	317400000	USD
CY2018Q4	us-gaap	Inventory Net InventoryNet	181100000	USD
CY2019	clf	Effectof Lifo Inventory Incrementon Financial Position EffectofLIFOInventoryIncrementonFinancialPosition	34200000	USD
CY2018	us-gaap	Effect Of Lifo Inventory Liquidation On Income EffectOfLIFOInventoryLiquidationOnIncome	200000	USD
CY2019Q4	us-gaap	Inventory Valuation Reserves InventoryValuationReserves	12700000	USD
CY2018Q4	us-gaap	Inventory Valuation Reserves InventoryValuationReserves	12600000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	3027400000	USD
CY2018Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	2308400000	USD
CY2019Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	1098400000	USD
CY2018Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	1022400000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	1929000000.0	USD
CY2018Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	1286000000.0	USD
CY2019	us-gaap	Depreciation Depreciation	76600000	USD
CY2018	us-gaap	Depreciation Depreciation	65600000	USD
CY2017	us-gaap	Depreciation Depreciation	65800000	USD
CY2019	us-gaap	Interest Costs Capitalized InterestCostsCapitalized	24800000	USD
CY2018	us-gaap	Interest Costs Capitalized InterestCostsCapitalized	6500000	USD
CY2019Q4	us-gaap	Land Land	12400000	USD
CY2018Q4	us-gaap	Land Land	12400000	USD
CY2019Q4	us-gaap	Mineral Properties Gross MineralPropertiesGross	537300000	USD
CY2018Q4	us-gaap	Mineral Properties Gross MineralPropertiesGross	537200000	USD
CY2019Q4	us-gaap	Mineral Properties Accumulated Depletion MineralPropertiesAccumulatedDepletion	134100000	USD
CY2018Q4	us-gaap	Mineral Properties Accumulated Depletion MineralPropertiesAccumulatedDepletion	126500000	USD
CY2019Q4	us-gaap	Mineral Properties Net MineralPropertiesNet	403200000	USD
CY2018Q4	us-gaap	Mineral Properties Net MineralPropertiesNet	410700000	USD
CY2019	us-gaap	Depletion Depletion	7500000	USD
CY2018	us-gaap	Depletion Depletion	7400000	USD
CY2017	us-gaap	Depletion Depletion	6800000	USD
CY2019Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	2113800000	USD
CY2018Q4	clf	Fair Value Adjustmentto Interest Rate Hedge FairValueAdjustmenttoInterestRateHedge	200000	USD
CY2018Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	2092900000	USD
CY2019	us-gaap	Extinguishment Of Debt Amount ExtinguishmentOfDebtAmount	724000000.0	USD
CY2019	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-18200000	USD
CY2018	us-gaap	Extinguishment Of Debt Amount ExtinguishmentOfDebtAmount	227400000	USD
CY2018	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-6800000	USD
CY2017	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	661300000	USD
CY2017	us-gaap	Extinguishment Of Debt Amount ExtinguishmentOfDebtAmount	1610700000	USD
CY2017	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-165400000	USD
CY2019Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Next Twelve Months LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths	0	USD
CY2019Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Two LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo	0	USD
CY2019Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Three LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree	0	USD
CY2019Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Four LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour	0	USD
CY2019Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive	400000000.0	USD
CY2019Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal After Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive	1838000000.0	USD
CY2019Q4	us-gaap	Debt Instrument Carrying Amount DebtInstrumentCarryingAmount	2238000000.0	USD
CY2019Q4	us-gaap	Cash And Cash Equivalents Fair Value Disclosure CashAndCashEquivalentsFairValueDisclosure	187600000	USD
CY2019Q4	us-gaap	Derivative Assets DerivativeAssets	45800000	USD
CY2019Q4	us-gaap	Assets Fair Value Disclosure AssetsFairValueDisclosure	233400000	USD
CY2019Q4	us-gaap	Derivative Liabilities DerivativeLiabilities	4300000	USD
CY2019Q4	us-gaap	Financial Liabilities Fair Value Disclosure FinancialLiabilitiesFairValueDisclosure	4300000	USD
CY2018Q4	us-gaap	Cash And Cash Equivalents Fair Value Disclosure CashAndCashEquivalentsFairValueDisclosure	543400000	USD
CY2018Q4	us-gaap	Derivative Assets DerivativeAssets	91500000	USD
CY2018Q4	us-gaap	Assets Fair Value Disclosure AssetsFairValueDisclosure	634900000	USD
CY2018Q4	us-gaap	Derivative Liabilities DerivativeLiabilities	3700000	USD
CY2018Q4	us-gaap	Financial Liabilities Fair Value Disclosure FinancialLiabilitiesFairValueDisclosure	3700000	USD
CY2019	clf	Defined Contribution Plan Eligible Amount Contributed Per Hour DefinedContributionPlanEligibleAmountContributedPerHour	0.60	USD
CY2019Q4	us-gaap	Defined Benefit Plan Accumulated Benefit Obligation DefinedBenefitPlanAccumulatedBenefitObligation	1010000000.0	USD
CY2018Q4	us-gaap	Defined Benefit Plan Accumulated Benefit Obligation DefinedBenefitPlanAccumulatedBenefitObligation	896800000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Health Care Cost Trend Rate Assumed Next Fiscal Year DefinedBenefitPlanHealthCareCostTrendRateAssumedNextFiscalYear	0.0650
CY2018Q4	us-gaap	Defined Benefit Plan Health Care Cost Trend Rate Assumed Next Fiscal Year DefinedBenefitPlanHealthCareCostTrendRateAssumedNextFiscalYear	0.0675
CY2019Q4	us-gaap	Defined Benefit Plan Ultimate Health Care Cost Trend Rate1 DefinedBenefitPlanUltimateHealthCareCostTrendRate1	0.0500
CY2018Q4	us-gaap	Defined Benefit Plan Ultimate Health Care Cost Trend Rate1 DefinedBenefitPlanUltimateHealthCareCostTrendRate1	0.0500
CY2019Q4	clf	Reserve For Investment Commitments ReserveForInvestmentCommitments	37100000	USD
CY2019	clf	Early Termination Feesfor Pension Benefits EarlyTerminationFeesforPensionBenefits	14900000	USD
CY2019	clf	Early Termination Feesfor Other Postretirement Benefits EarlyTerminationFeesforOtherPostretirementBenefits	3000000.0	USD
CY2018	us-gaap	Defined Benefit Plan Contributions By Employer DefinedBenefitPlanContributionsByEmployer	3800000	USD
CY2019	us-gaap	Defined Benefit Plan Contributions By Employer DefinedBenefitPlanContributionsByEmployer	3700000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Expected Future Employer Contributions Next Fiscal Year DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear	3500000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Expected Amortization Of Gain Loss Next Fiscal Year DefinedBenefitPlanExpectedAmortizationOfGainLossNextFiscalYear	8000000.0	USD
CY2019	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	3700000	USD
CY2018	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	0	USD
CY2017	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	0	USD
CY2019	us-gaap	Allocated Share Based Compensation Expense Net Of Tax AllocatedShareBasedCompensationExpenseNetOfTax	13900000	USD
CY2018	us-gaap	Allocated Share Based Compensation Expense Net Of Tax AllocatedShareBasedCompensationExpenseNetOfTax	15100000	USD
CY2017	us-gaap	Allocated Share Based Compensation Expense Net Of Tax AllocatedShareBasedCompensationExpenseNetOfTax	18200000	USD
CY2015Q1	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	412710	shares
CY2015Q1	clf	Share Based Compensation Arrangement By Share Based Payment Award Grant Date Price ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDatePrice	7.70
CY2014Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	250000	shares
CY2014Q4	clf	Share Based Compensation Arrangement By Share Based Payment Award Grant Date Price ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDatePrice	13.83
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber	563230	shares
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice	10.42
CY2019Q4	us-gaap	Common Stock Capital Shares Reserved For Future Issuance CommonStockCapitalSharesReservedForFutureIssuance	10321432	shares
CY2018Q4	clf	Sharebased Compensation Arrangement Award Vestedand Expectedto Vest Outstanding Number SharebasedCompensationArrangementAwardVestedandExpectedtoVestOutstandingNumber	6792201	shares
CY2018Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue	6.90
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod	1285419	shares
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	14.18
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod	3199270	shares
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue	2.20
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeited In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod	121923	shares
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeitures Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue	12.21
CY2019Q4	clf	Sharebased Compensation Arrangement Award Vestedand Expectedto Vest Outstanding Number SharebasedCompensationArrangementAwardVestedandExpectedtoVestOutstandingNumber	4756427	shares
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue	11.90
CY2019Q4	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized	16000000.0	USD
CY2019	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1 EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1	P1Y2M12D
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	311900000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	565000000.0	USD
CY2017	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	90700000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	200000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	-300000	USD
CY2017	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	17500000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	312100000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	564700000	USD
CY2017	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	108200000	USD
CY2019	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	-700000	USD
CY2018	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	-500000	USD
CY2017	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	-252600000	USD
CY2019	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	100000	USD
CY2018	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	0	USD
CY2017	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	-100000	USD
CY2019	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	200000	USD
CY2018	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	700000	USD
CY2017	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	300000	USD
CY2019	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	-400000	USD
CY2018	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	200000	USD
CY2017	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	-252400000	USD
CY2019	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	18000000.0	USD
CY2018	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-475400000	USD
CY2017	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	0	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	17600000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-475200000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-252400000	USD
CY2019	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	65500000	USD
CY2019	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2018	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	118600000	USD
CY2018	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2017	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	37900000	USD
CY2017	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.350
CY2019	us-gaap	Income Tax Reconciliation Nondeductible Expense Depletion IncomeTaxReconciliationNondeductibleExpenseDepletion	-49300000	USD
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Nondeductible Expense Depletion EffectiveIncomeTaxRateReconciliationNondeductibleExpenseDepletion	-0.158
CY2018	us-gaap	Income Tax Reconciliation Nondeductible Expense Depletion IncomeTaxReconciliationNondeductibleExpenseDepletion	-54600000	USD
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Nondeductible Expense Depletion EffectiveIncomeTaxRateReconciliationNondeductibleExpenseDepletion	-0.097
CY2017	us-gaap	Income Tax Reconciliation Nondeductible Expense Depletion IncomeTaxReconciliationNondeductibleExpenseDepletion	-61600000	USD
CY2017	us-gaap	Effective Income Tax Rate Reconciliation Nondeductible Expense Depletion EffectiveIncomeTaxRateReconciliationNondeductibleExpenseDepletion	-0.569
CY2019	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	0	USD
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Change In Enacted Tax Rate EffectiveIncomeTaxRateReconciliationChangeInEnactedTaxRate	0
CY2018	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	0	USD
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Change In Enacted Tax Rate EffectiveIncomeTaxRateReconciliationChangeInEnactedTaxRate	0
CY2017	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	407500000	USD
CY2017	us-gaap	Effective Income Tax Rate Reconciliation Change In Enacted Tax Rate EffectiveIncomeTaxRateReconciliationChangeInEnactedTaxRate	3.766
CY2019	us-gaap	Income Tax Reconciliation Disposition Of Business IncomeTaxReconciliationDispositionOfBusiness	846000000.0	USD
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Disposition Of Business EffectiveIncomeTaxRateReconciliationDispositionOfBusiness	2.711
CY2018	us-gaap	Income Tax Reconciliation Disposition Of Business IncomeTaxReconciliationDispositionOfBusiness	161700000	USD
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Disposition Of Business EffectiveIncomeTaxRateReconciliationDispositionOfBusiness	0.286
CY2017	us-gaap	Income Tax Reconciliation Disposition Of Business IncomeTaxReconciliationDispositionOfBusiness	0	USD
CY2017	us-gaap	Effective Income Tax Rate Reconciliation Disposition Of Business EffectiveIncomeTaxRateReconciliationDispositionOfBusiness	0
CY2019	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	200000	USD
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Foreign Income Tax Rate Differential EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential	0.001
CY2018	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	100000	USD
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Foreign Income Tax Rate Differential EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential	0
CY2017	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	477900000	USD
CY2017	us-gaap	Effective Income Tax Rate Reconciliation Foreign Income Tax Rate Differential EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential	4.417
CY2019	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	1200000	USD
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0.004
CY2018	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	800000	USD
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0.002
CY2017	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-1500000	USD
CY2017	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	-0.014
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	17600000	USD
CY2019	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.057
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-475200000	USD
CY2018	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	-0.841
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-252400000	USD
CY2017	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	-2.333
CY2019	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.21
CY2017	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.350
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-11400000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-3600000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	0	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax	100000	USD
CY2018	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax	700000	USD
CY2017	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax	0	USD
CY2019	us-gaap	Other Comprehensive Income Loss Tax Portion Attributable To Parent1 OtherComprehensiveIncomeLossTaxPortionAttributableToParent1	11500000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Tax Portion Attributable To Parent1 OtherComprehensiveIncomeLossTaxPortionAttributableToParent1	4300000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Tax Portion Attributable To Parent1 OtherComprehensiveIncomeLossTaxPortionAttributableToParent1	0	USD
CY2019Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	794900000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	2118800000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Pensions DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPensions	113700000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Pensions DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPensions	102800000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Deferred Income DeferredTaxAssetsDeferredIncome	25200000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Deferred Income DeferredTaxAssetsDeferredIncome	23300000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Property Plant And Equipment DeferredTaxAssetsPropertyPlantAndEquipment	1400000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Property Plant And Equipment DeferredTaxAssetsPropertyPlantAndEquipment	13300000	USD
CY2019Q4	us-gaap	Deferred Tax Assets State Taxes DeferredTaxAssetsStateTaxes	71000000.0	USD
CY2018Q4	us-gaap	Deferred Tax Assets State Taxes DeferredTaxAssetsStateTaxes	68200000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Other DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsOther	45100000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Other DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsOther	48400000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	1051300000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	2374800000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	441300000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	1287300000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	610000000.0	USD
CY2018Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	1087500000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Investments DeferredTaxLiabilitiesInvestments	136800000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Investments DeferredTaxLiabilitiesInvestments	141200000	USD
CY2019Q4	clf	Deferred Tax Liabilities Intercompany Notes DeferredTaxLiabilitiesIntercompanyNotes	0	USD
CY2018Q4	clf	Deferred Tax Liabilities Intercompany Notes DeferredTaxLiabilitiesIntercompanyNotes	465700000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	13700000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	15800000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	150500000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	622700000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	459500000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	464800000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards Domestic DeferredTaxAssetsOperatingLossCarryforwardsDomestic	3500000000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards Foreign DeferredTaxAssetsOperatingLossCarryforwardsForeign	1600000000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards Domestic DeferredTaxAssetsOperatingLossCarryforwardsDomestic	3600000000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards Foreign DeferredTaxAssetsOperatingLossCarryforwardsForeign	6600000000	USD
CY2019Q4	us-gaap	Deferred Tax Asset Interest Carryforward DeferredTaxAssetInterestCarryforward	55300000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	1287300000	USD
CY2017Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	1983100000	USD
CY2016Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	3095100000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	441300000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	1287300000	USD
CY2017Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	1983100000	USD
CY2018	us-gaap	Valuation Allowance Deferred Tax Asset Change In Amount ValuationAllowanceDeferredTaxAssetChangeInAmount	-695800000	USD
CY2019	clf	Estimated Taxable Incometo Fully Utilize Deferred Tax Assets EstimatedTaxableIncometoFullyUtilizeDeferredTaxAssets	109000000.0	USD
CY2019Q4	us-gaap	Undistributed Earnings Of Foreign Subsidiaries UndistributedEarningsOfForeignSubsidiaries	0	USD
CY2018Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	29000000.0	USD
CY2017Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	33500000	USD
CY2016Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	30700000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	200000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	100000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	2800000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	0	USD
CY2018	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	3600000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	4500000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	0	USD
CY2018	us-gaap	Unrecognized Tax Benefits Increases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsIncreasesResultingFromSettlementsWithTaxingAuthorities	0	USD
CY2017	us-gaap	Unrecognized Tax Benefits Increases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsIncreasesResultingFromSettlementsWithTaxingAuthorities	1000000.0	USD
CY2019	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	0	USD
CY2018	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	8200000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	0	USD
CY2019	us-gaap	Unrecognized Tax Benefits Period Increase Decrease UnrecognizedTaxBenefitsPeriodIncreaseDecrease	0	USD
CY2018	us-gaap	Unrecognized Tax Benefits Period Increase Decrease UnrecognizedTaxBenefitsPeriodIncreaseDecrease	0	USD
CY2017	us-gaap	Unrecognized Tax Benefits Period Increase Decrease UnrecognizedTaxBenefitsPeriodIncreaseDecrease	100000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	29200000	USD
CY2018Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	29000000.0	USD
CY2017Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	33500000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	29200000	USD
CY2018Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	29000000.0	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	29200000	USD
CY2019Q4	us-gaap	Accrual For Environmental Loss Contingencies AccrualForEnvironmentalLossContingencies	2000000.0	USD
CY2018Q4	us-gaap	Accrual For Environmental Loss Contingencies AccrualForEnvironmentalLossContingencies	2500000	USD
CY2019Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	165300000	USD
CY2018Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	172400000	USD
CY2019Q4	clf	Environmental Loss Contingency And Mine Reclamation And Closing Liability Current And Noncurrent EnvironmentalLossContingencyAndMineReclamationAndClosingLiabilityCurrentAndNoncurrent	167300000	USD
CY2018Q4	clf	Environmental Loss Contingency And Mine Reclamation And Closing Liability Current And Noncurrent EnvironmentalLossContingencyAndMineReclamationAndClosingLiabilityCurrentAndNoncurrent	174900000	USD
CY2019Q4	us-gaap	Accrued Reclamation Costs Current AccruedReclamationCostsCurrent	2400000	USD
CY2018Q4	us-gaap	Accrued Reclamation Costs Current AccruedReclamationCostsCurrent	2900000	USD
CY2019Q4	us-gaap	Mine Reclamation And Closing Liability Noncurrent MineReclamationAndClosingLiabilityNoncurrent	164900000	USD
CY2018Q4	us-gaap	Mine Reclamation And Closing Liability Noncurrent MineReclamationAndClosingLiabilityNoncurrent	172000000.0	USD
CY2018Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	172400000	USD
CY2017Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	168400000	USD
CY2019	us-gaap	Asset Retirement Obligation Accretion Expense AssetRetirementObligationAccretionExpense	10100000	USD
CY2018	us-gaap	Asset Retirement Obligation Accretion Expense AssetRetirementObligationAccretionExpense	9500000	USD
CY2019	us-gaap	Asset Retirement Obligation Liabilities Settled AssetRetirementObligationLiabilitiesSettled	800000	USD
CY2018	us-gaap	Asset Retirement Obligation Liabilities Settled AssetRetirementObligationLiabilitiesSettled	1000000.0	USD
CY2019	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	-16400000	USD
CY2018	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	-4500000	USD
CY2019Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	165300000	USD
CY2018Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	172400000	USD
CY2019	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	-16400000	USD
CY2019Q4	us-gaap	Derivative Assets DerivativeAssets	45800000	USD
CY2018Q4	us-gaap	Derivative Assets DerivativeAssets	91500000	USD
CY2019Q4	us-gaap	Derivative Liabilities DerivativeLiabilities	4300000	USD
CY2018Q4	us-gaap	Derivative Liabilities DerivativeLiabilities	3700000	USD
CY2019	us-gaap	Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet	7500000	USD
CY2018	us-gaap	Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet	422600000	USD
CY2017	us-gaap	Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet	119300000	USD
CY2019	us-gaap	Income Loss From Discontinued Operations Net Of Tax IncomeLossFromDiscontinuedOperationsNetOfTax	-1700000	USD
CY2018	us-gaap	Income Loss From Discontinued Operations Net Of Tax IncomeLossFromDiscontinuedOperationsNetOfTax	88200000	USD
CY2017	us-gaap	Income Loss From Discontinued Operations Net Of Tax IncomeLossFromDiscontinuedOperationsNetOfTax	2500000	USD
CY2018Q4	us-gaap	Stock Repurchase Program Authorized Amount1 StockRepurchaseProgramAuthorizedAmount1	200000000	USD
CY2019Q2	us-gaap	Stock Repurchase Program Authorized Amount1 StockRepurchaseProgramAuthorizedAmount1	100000000	USD
CY2019	us-gaap	Stock Repurchased During Period Shares StockRepurchasedDuringPeriodShares	24400000	shares
CY2019	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	252900000	USD
CY2018	us-gaap	Stock Repurchased During Period Shares StockRepurchasedDuringPeriodShares	5400000	shares
CY2018	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	47500000	USD
CY2019Q4	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.06
CY2019Q4	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.10
CY2019Q3	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.06
CY2019Q2	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.05
CY2019Q1	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.05
CY2017	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	661300000	USD
CY2019Q4	us-gaap	Aoci Before Tax Attributable To Parent AociBeforeTaxAttributableToParent	-458000000.0	USD
CY2019Q4	us-gaap	Aoci Tax Attributable To Parent AociTaxAttributableToParent	-139200000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-318800000	USD
CY2018Q4	us-gaap	Aoci Before Tax Attributable To Parent AociBeforeTaxAttributableToParent	-411600000	USD
CY2018Q4	us-gaap	Aoci Tax Attributable To Parent AociTaxAttributableToParent	-127700000	USD
CY2018Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-283900000	USD
CY2017Q4	us-gaap	Aoci Before Tax Attributable To Parent AociBeforeTaxAttributableToParent	-162400000	USD
CY2017Q4	us-gaap	Aoci Tax Attributable To Parent AociTaxAttributableToParent	-123400000	USD
CY2017Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-39000000.0	USD
CY2016Q4	us-gaap	Accumulated Other Comprehensive Income Loss Defined Benefit Pension And Other Postretirement Plans Net Of Tax AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax	-260600000	USD
CY2016Q4	us-gaap	Accumulated Other Comprehensive Income Loss Foreign Currency Translation Adjustment Net Of Tax AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax	239300000	USD
CY2016Q4	us-gaap	Accumulated Other Comprehensive Income Loss Cumulative Changes In Net Gain Loss From Cash Flow Hedges Effect Net Of Tax AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax	0	USD
CY2016Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-21300000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	-44200000	USD
CY2017	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	26500000	USD
CY2017Q4	us-gaap	Accumulated Other Comprehensive Income Loss Defined Benefit Pension And Other Postretirement Plans Net Of Tax AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax	-263900000	USD
CY2017Q4	us-gaap	Accumulated Other Comprehensive Income Loss Foreign Currency Translation Adjustment Net Of Tax AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax	225400000	USD
CY2017Q4	us-gaap	Accumulated Other Comprehensive Income Loss Cumulative Changes In Net Gain Loss From Cash Flow Hedges Effect Net Of Tax AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax	-500000	USD
CY2017Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-39000000.0	USD
CY2018	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	-40800000	USD
CY2018	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-204100000	USD
CY2018Q4	us-gaap	Accumulated Other Comprehensive Income Loss Defined Benefit Pension And Other Postretirement Plans Net Of Tax AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax	-281100000	USD
CY2018Q4	us-gaap	Accumulated Other Comprehensive Income Loss Foreign Currency Translation Adjustment Net Of Tax AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax	0	USD
CY2018Q4	us-gaap	Accumulated Other Comprehensive Income Loss Cumulative Changes In Net Gain Loss From Cash Flow Hedges Effect Net Of Tax AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax	-2800000	USD
CY2018Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-283900000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	-59000000.0	USD
CY2019	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	24100000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Defined Benefit Pension And Other Postretirement Plans Net Of Tax AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax	-315700000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Foreign Currency Translation Adjustment Net Of Tax AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax	0	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Cumulative Changes In Net Gain Loss From Cash Flow Hedges Effect Net Of Tax AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax	-3100000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-318800000	USD
CY2019Q4	us-gaap	Related Party Transaction Due From To Related Party RelatedPartyTransactionDueFromToRelatedParty	73600000	USD
CY2018Q4	us-gaap	Related Party Transaction Due From To Related Party RelatedPartyTransactionDueFromToRelatedParty	220000000.0	USD
CY2019	us-gaap	Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest	294500000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest	1039900000	USD
CY2017	us-gaap	Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest	360600000	USD
CY2019	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	0	USD
CY2018	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	0	USD
CY2017	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	-3900000	USD
CY2019	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	294500000	USD
CY2018	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	1039900000	USD
CY2017	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	364500000	USD
CY2019	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	-1700000	USD
CY2018	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	88200000	USD
CY2017	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	2500000	USD
CY2019	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	292800000	USD
CY2018	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	1128100000	USD
CY2017	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	367000000.0	USD
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	276800000	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	297200000	shares
CY2017	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	288400000	shares
CY2019	us-gaap	Incremental Common Shares Attributable To Conversion Of Debt Securities IncrementalCommonSharesAttributableToConversionOfDebtSecurities	4400000	shares
CY2018	us-gaap	Incremental Common Shares Attributable To Conversion Of Debt Securities IncrementalCommonSharesAttributableToConversionOfDebtSecurities	3400000	shares
CY2017	us-gaap	Incremental Common Shares Attributable To Conversion Of Debt Securities IncrementalCommonSharesAttributableToConversionOfDebtSecurities	0	shares
CY2019	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	3300000	shares
CY2018	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	3500000	shares
CY2017	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	4600000	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	284500000	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	304100000	shares
CY2017	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	293000000.0	shares
CY2019	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	1.07
CY2018	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	3.50
CY2017	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	1.27
CY2019	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	-0.01
CY2018	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	0.30
CY2017	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	0.01
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.06
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.80
CY2017	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.28
CY2019	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	1.04
CY2018	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	3.42
CY2017	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	1.25
CY2019	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	-0.01
CY2018	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	0.29
CY2017	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	0.01
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.03
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.71
CY2017	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.26
CY2017	us-gaap	Incremental Common Shares Attributable To Conversion Of Debt Securities IncrementalCommonSharesAttributableToConversionOfDebtSecurities	0	shares
CY2019Q4	clf	Estimated Project Capital Expenditures EstimatedProjectCapitalExpenditures	830000000	USD
CY2019Q4	clf	Project Spend Contingency Percentage ProjectSpendContingencyPercentage	0.20
CY2019Q4	us-gaap	Unrecorded Unconditional Purchase Obligation Balance On First Anniversary UnrecordedUnconditionalPurchaseObligationBalanceOnFirstAnniversary	290000000	USD
CY2019Q4	us-gaap	Accrual For Environmental Loss Contingencies AccrualForEnvironmentalLossContingencies	2000000.0	USD
CY2018Q4	us-gaap	Accrual For Environmental Loss Contingencies AccrualForEnvironmentalLossContingencies	2500000	USD
CY2019Q1	us-gaap	Revenues Revenues	157000000.0	USD
CY2019Q2	us-gaap	Revenues Revenues	743200000	USD
CY2019Q3	us-gaap	Revenues Revenues	555600000	USD
CY2019Q4	us-gaap	Revenues Revenues	534100000	USD
CY2019	us-gaap	Revenues Revenues	1989900000	USD
CY2019Q1	us-gaap	Gross Profit GrossProfit	30900000	USD
CY2019Q2	us-gaap	Gross Profit GrossProfit	263000000.0	USD
CY2019Q3	us-gaap	Gross Profit GrossProfit	154900000	USD
CY2019Q4	us-gaap	Gross Profit GrossProfit	126900000	USD
CY2019	us-gaap	Gross Profit GrossProfit	575700000	USD
CY2019Q1	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	-22100000	USD
CY2019Q2	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	161400000	USD
CY2019Q3	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	91800000	USD
CY2019Q4	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	63400000	USD
CY2019	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	294500000	USD
CY2019Q1	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	0	USD
CY2019Q2	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	-600000	USD
CY2019Q3	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	-900000	USD
CY2019Q4	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	-200000	USD
CY2019	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	-1700000	USD
CY2019Q1	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	-22100000	USD
CY2019Q2	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	160800000	USD
CY2019Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	90900000	USD
CY2019Q4	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	63200000	USD
CY2019	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	292800000	USD
CY2019Q1	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	-0.08
CY2019Q2	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	0.59
CY2019Q3	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	0.34
CY2019Q4	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	0.23
CY2019	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	1.07
CY2019Q1	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	0
CY2019Q2	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	0
CY2019Q3	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	0
CY2019Q4	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	0
CY2019	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	-0.01
CY2019Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-0.08
CY2019Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.59
CY2019Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.34
CY2019Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.23
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.06
CY2019Q1	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	-0.08
CY2019Q2	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	0.57
CY2019Q3	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	0.33
CY2019Q4	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	0.23
CY2019	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	1.04
CY2019Q1	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	0
CY2019Q2	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	0
CY2019Q3	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	0
CY2019Q4	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	0
CY2019	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	-0.01
CY2019Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-0.08
CY2019Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.57
CY2019Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.33
CY2019Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.23
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.03
CY2018Q1	us-gaap	Revenues Revenues	180000000.0	USD
CY2018Q2	us-gaap	Revenues Revenues	714300000	USD
CY2018Q3	us-gaap	Revenues Revenues	741800000	USD
CY2018Q4	us-gaap	Revenues Revenues	696300000	USD
CY2018	us-gaap	Revenues Revenues	2332400000	USD
CY2018Q1	us-gaap	Gross Profit GrossProfit	61500000	USD
CY2018Q2	us-gaap	Gross Profit GrossProfit	284500000	USD
CY2018Q3	us-gaap	Gross Profit GrossProfit	261600000	USD
CY2018Q4	us-gaap	Gross Profit GrossProfit	202000000.0	USD
CY2018	us-gaap	Gross Profit GrossProfit	809600000	USD
CY2018Q1	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	-13400000	USD
CY2018Q2	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	229400000	USD
CY2018Q3	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	199800000	USD
CY2018Q4	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	624100000	USD
CY2018	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	1039900000	USD
CY2018Q1	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	-70900000	USD
CY2018Q2	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	-64300000	USD
CY2018Q3	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	238000000.0	USD
CY2018Q4	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	-14600000	USD
CY2018	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	88200000	USD
CY2018Q1	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	-84300000	USD
CY2018Q2	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	165100000	USD
CY2018Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	437800000	USD
CY2018Q4	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	609500000	USD
CY2018	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	1128100000	USD
CY2018Q1	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	-0.05
CY2018Q2	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	0.77
CY2018Q3	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	0.67
CY2018Q4	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	2.11
CY2018	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	3.50
CY2018Q1	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	-0.24
CY2018Q2	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	-0.22
CY2018Q3	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	0.80
CY2018Q4	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	-0.05
CY2018	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	0.30
CY2018Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-0.29
CY2018Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.55
CY2018Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.47
CY2018Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.06
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.80
CY2018Q1	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	-0.05
CY2018Q2	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	0.76
CY2018Q3	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	0.64
CY2018Q4	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	2.03
CY2018	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	3.42
CY2018Q1	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	-0.24
CY2018Q2	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	-0.21
CY2018Q3	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	0.77
CY2018Q4	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	-0.05
CY2018	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	0.29
CY2018Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-0.29
CY2018Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.55
CY2018Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.41
CY2018Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.98
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.71
CY2019Q4	us-gaap	Minority Interest Ownership Percentage By Parent MinorityInterestOwnershipPercentageByParent	1
CY2019Q4	us-gaap	Minority Interest Ownership Percentage By Parent MinorityInterestOwnershipPercentageByParent	1
CY2019Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	352600000	USD
CY2019Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	94000000.0	USD
CY2019Q4	us-gaap	Inventory Net InventoryNet	317400000	USD
CY2019Q4	us-gaap	Derivative Assets Current DerivativeAssetsCurrent	45800000	USD
CY2019Q4	us-gaap	Income Taxes Receivable IncomeTaxesReceivable	58600000	USD
CY2019Q4	us-gaap	Other Assets Current OtherAssetsCurrent	29500000	USD
CY2019Q4	us-gaap	Assets Current AssetsCurrent	897900000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	1929000000.0	USD
CY2019Q4	us-gaap	Income Taxes Receivable Noncurrent IncomeTaxesReceivableNoncurrent	62700000	USD
CY2019Q4	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	459500000	USD
CY2019Q4	clf	Investmentinsubsidiaries Investmentinsubsidiaries	0	USD
CY2019Q4	clf	Longtermintercompanynotes Longtermintercompanynotes	0	USD
CY2019Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	154700000	USD
CY2019Q4	us-gaap	Assets Assets	3503800000	USD
CY2019Q4	us-gaap	Accounts Payable Current AccountsPayableCurrent	193200000	USD
CY2019Q4	us-gaap	Accrued Liabilities Current AccruedLiabilitiesCurrent	126300000	USD
CY2019Q4	us-gaap	Taxes Payable Current TaxesPayableCurrent	37900000	USD
CY2019Q4	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	52000000.0	USD
CY2019Q4	us-gaap	Liabilities Current LiabilitiesCurrent	409400000	USD
CY2019Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	2113800000	USD
CY2019Q4	us-gaap	Pension And Other Postretirement Defined Benefit Plans Liabilities Noncurrent PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent	311500000	USD
CY2019Q4	us-gaap	Mine Reclamation And Closing Liability Noncurrent MineReclamationAndClosingLiabilityNoncurrent	164900000	USD
CY2019Q4	clf	Longtermintercompanynotespayable Longtermintercompanynotespayable	0	USD
CY2019Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	146300000	USD
CY2019Q4	us-gaap	Liabilities Liabilities	3145900000	USD
CY2019Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	357900000	USD
CY2019Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	3503800000	USD
CY2018Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	823200000	USD
CY2018Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	226700000	USD
CY2018Q4	us-gaap	Inventory Net InventoryNet	181100000	USD
CY2018Q4	us-gaap	Derivative Assets Current DerivativeAssetsCurrent	91500000	USD
CY2018Q4	us-gaap	Income Taxes Receivable IncomeTaxesReceivable	117300000	USD
CY2018Q4	us-gaap	Other Assets Current OtherAssetsCurrent	39800000	USD
CY2018Q4	us-gaap	Assets Current AssetsCurrent	1479600000	USD
CY2018Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	1286000000.0	USD
CY2018Q4	us-gaap	Income Taxes Receivable Noncurrent IncomeTaxesReceivableNoncurrent	121300000	USD
CY2018Q4	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	464800000	USD
CY2018Q4	clf	Investmentinsubsidiaries Investmentinsubsidiaries	0	USD
CY2018Q4	clf	Longtermintercompanynotes Longtermintercompanynotes	0	USD
CY2018Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	177900000	USD
CY2018Q4	us-gaap	Assets Assets	3529600000	USD
CY2018Q4	us-gaap	Accounts Payable Current AccountsPayableCurrent	186800000	USD
CY2018Q4	us-gaap	Accrued Liabilities Current AccruedLiabilitiesCurrent	158900000	USD
CY2018Q4	us-gaap	Taxes Payable Current TaxesPayableCurrent	35500000	USD
CY2018Q4	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	87000000.0	USD
CY2018Q4	us-gaap	Liabilities Current LiabilitiesCurrent	468200000	USD
CY2018Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	2092900000	USD
CY2018Q4	us-gaap	Pension And Other Postretirement Defined Benefit Plans Liabilities Noncurrent PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent	248700000	USD
CY2018Q4	us-gaap	Mine Reclamation And Closing Liability Noncurrent MineReclamationAndClosingLiabilityNoncurrent	172000000.0	USD
CY2018Q4	clf	Longtermintercompanynotespayable Longtermintercompanynotespayable	0	USD
CY2018Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	123600000	USD
CY2018Q4	us-gaap	Liabilities Liabilities	3105400000	USD
CY2018Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	424200000	USD
CY2018Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	3529600000	USD
CY2019	us-gaap	Revenues Revenues	1989900000	USD
CY2019	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	1414200000	USD
CY2019	us-gaap	Gross Profit GrossProfit	575700000	USD
CY2019	us-gaap	Selling General And Administrative Expense SellingGeneralAndAdministrativeExpense	119400000	USD
CY2019	us-gaap	Other Operating Income Expense Net OtherOperatingIncomeExpenseNet	-27000000.0	USD
CY2019	us-gaap	Operating Expenses OperatingExpenses	146400000	USD
CY2019	us-gaap	Operating Income Loss OperatingIncomeLoss	429300000	USD
CY2019	us-gaap	Interest Income Expense Nonoperating Net InterestIncomeExpenseNonoperatingNet	-101200000	USD
CY2019	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-18200000	USD
CY2019	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	2200000	USD
CY2019	us-gaap	Nonoperating Income Expense NonoperatingIncomeExpense	-117200000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	312100000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	17600000	USD
CY2019	us-gaap	Income Loss From Subsidiaries Net Of Tax IncomeLossFromSubsidiariesNetOfTax	0	USD
CY2019	us-gaap	Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest	294500000	USD
CY2019	us-gaap	Income Loss From Discontinued Operations Net Of Tax IncomeLossFromDiscontinuedOperationsNetOfTax	-1700000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	292800000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-34900000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	257900000	USD
CY2018	us-gaap	Revenues Revenues	2332400000	USD
CY2018	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	1522800000	USD
CY2018	us-gaap	Gross Profit GrossProfit	809600000	USD
CY2018	us-gaap	Selling General And Administrative Expense SellingGeneralAndAdministrativeExpense	113500000	USD
CY2018	us-gaap	Other Operating Income Expense Net OtherOperatingIncomeExpenseNet	-22900000	USD
CY2018	us-gaap	Operating Expenses OperatingExpenses	136400000	USD
CY2018	us-gaap	Operating Income Loss OperatingIncomeLoss	673200000	USD
CY2018	us-gaap	Interest Income Expense Nonoperating Net InterestIncomeExpenseNonoperatingNet	-118900000	USD
CY2018	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-6800000	USD
CY2018	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	17200000	USD
CY2018	us-gaap	Nonoperating Income Expense NonoperatingIncomeExpense	-108500000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	564700000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-475200000	USD
CY2018	us-gaap	Income Loss From Subsidiaries Net Of Tax IncomeLossFromSubsidiariesNetOfTax	0	USD
CY2018	us-gaap	Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest	1039900000	USD
CY2018	us-gaap	Income Loss From Discontinued Operations Net Of Tax IncomeLossFromDiscontinuedOperationsNetOfTax	88200000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	1128100000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-244900000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	883200000	USD
CY2017	us-gaap	Revenues Revenues	1866000000.0	USD
CY2017	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	1398400000	USD
CY2017	us-gaap	Gross Profit GrossProfit	467600000	USD
CY2017	us-gaap	Selling General And Administrative Expense SellingGeneralAndAdministrativeExpense	102900000	USD
CY2017	us-gaap	Other Operating Income Expense Net OtherOperatingIncomeExpenseNet	25500000	USD
CY2017	us-gaap	Operating Expenses OperatingExpenses	77400000	USD
CY2017	us-gaap	Operating Income Loss OperatingIncomeLoss	390200000	USD
CY2017	us-gaap	Interest Income Expense Nonoperating Net InterestIncomeExpenseNonoperatingNet	-126800000	USD
CY2017	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-165400000	USD
CY2017	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	10200000	USD
CY2017	us-gaap	Nonoperating Income Expense NonoperatingIncomeExpense	-282000000.0	USD
CY2017	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	108200000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-252400000	USD
CY2017	us-gaap	Income Loss From Subsidiaries Net Of Tax IncomeLossFromSubsidiariesNetOfTax	0	USD
CY2017	us-gaap	Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest	360600000	USD
CY2017	us-gaap	Income Loss From Discontinued Operations Net Of Tax IncomeLossFromDiscontinuedOperationsNetOfTax	2500000	USD
CY2017	us-gaap	Profit Loss ProfitLoss	363100000	USD
CY2017	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	-3900000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	367000000.0	USD
CY2017	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-4000000.0	USD
CY2017	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	363000000.0	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	562500000	USD
CY2019	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	639000000.0	USD
CY2019	clf	Paymentsfor Deposits On Property Plantand Equipment PaymentsforDepositsOnPropertyPlantandEquipment	17000000.0	USD
CY2019	clf	Intercompanyinvestments Intercompanyinvestments	0	USD
CY2019	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-11600000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-644400000	USD
CY2019	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	252900000	USD
CY2019	us-gaap	Payments Of Dividends PaymentsOfDividends	72100000	USD
CY2019	us-gaap	Proceeds From Issuance Of Senior Long Term Debt ProceedsFromIssuanceOfSeniorLongTermDebt	720900000	USD
CY2019	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	6800000	USD
CY2019	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	729300000	USD
CY2019	us-gaap	Payments Of Distributions To Affiliates PaymentsOfDistributionsToAffiliates	44200000	USD
CY2019	clf	Intercompanyfinancing Intercompanyfinancing	0	USD
CY2019	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-9700000	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-394100000	USD
CY2019	us-gaap	Effect Of Exchange Rate On Cash And Cash Equivalents EffectOfExchangeRateOnCashAndCashEquivalents	0	USD
CY2019	clf	Increase Decreasein Cashand Cash Equivalents Including Cash Classified Within Other Current Assets Relatedto Discontinued Operations IncreaseDecreaseinCashandCashEquivalentsIncludingCashClassifiedWithinOtherCurrentAssetsRelatedtoDiscontinuedOperations	-476000000.0	USD
CY2019	us-gaap	Net Cash Provided By Used In Discontinued Operations NetCashProvidedByUsedInDiscontinuedOperations	5400000	USD
CY2019	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	-470600000	USD
CY2018Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	823200000	USD
CY2019Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	352600000	USD
CY2018	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	478500000	USD
CY2018	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	208600000	USD
CY2018	clf	Paymentsfor Deposits On Property Plantand Equipment PaymentsforDepositsOnPropertyPlantandEquipment	87500000	USD
CY2018	clf	Intercompanyinvestments Intercompanyinvestments	0	USD
CY2018	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-23000000.0	USD
CY2018	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-273100000	USD
CY2018	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	47500000	USD
CY2018	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	1500000	USD
CY2018	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	234500000	USD
CY2018	us-gaap	Payments Of Distributions To Affiliates PaymentsOfDistributionsToAffiliates	44200000	USD
CY2018	clf	Intercompanyfinancing Intercompanyfinancing	0	USD
CY2018	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-47500000	USD
CY2018	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-375200000	USD
CY2018	us-gaap	Effect Of Exchange Rate On Cash And Cash Equivalents EffectOfExchangeRateOnCashAndCashEquivalents	-2300000	USD
CY2018	clf	Increase Decreasein Cashand Cash Equivalents Including Cash Classified Within Other Current Assets Relatedto Discontinued Operations IncreaseDecreaseinCashandCashEquivalentsIncludingCashClassifiedWithinOtherCurrentAssetsRelatedtoDiscontinuedOperations	-172100000	USD
CY2018	us-gaap	Net Cash Provided By Used In Discontinued Operations NetCashProvidedByUsedInDiscontinuedOperations	17000000.0	USD
CY2018	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	-155100000	USD
CY2017Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	978300000	USD
CY2018Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	823200000	USD
CY2017	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	338100000	USD
CY2017	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	134900000	USD
CY2017	clf	Paymentsfor Deposits On Property Plantand Equipment PaymentsforDepositsOnPropertyPlantandEquipment	16800000	USD
CY2017	clf	Intercompanyinvestments Intercompanyinvestments	0	USD
CY2017	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	4300000	USD
CY2017	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-156000000.0	USD
CY2017	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	661300000	USD
CY2017	us-gaap	Proceeds From Issuance Of Senior Long Term Debt ProceedsFromIssuanceOfSeniorLongTermDebt	1771500000	USD
CY2017	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	28600000	USD
CY2017	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	1720700000	USD
CY2017	us-gaap	Payments For Repurchase Of Redeemable Noncontrolling Interest PaymentsForRepurchaseOfRedeemableNoncontrollingInterest	105000000.0	USD
CY2017	us-gaap	Payments Of Distributions To Affiliates PaymentsOfDistributionsToAffiliates	52900000	USD
CY2017	clf	Intercompanyfinancing Intercompanyfinancing	0	USD
CY2017	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-26700000	USD
CY2017	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	498900000	USD
CY2017	us-gaap	Effect Of Exchange Rate On Cash And Cash Equivalents EffectOfExchangeRateOnCashAndCashEquivalents	3300000	USD
CY2017	clf	Increase Decreasein Cashand Cash Equivalents Including Cash Classified Within Other Current Assets Relatedto Discontinued Operations IncreaseDecreaseinCashandCashEquivalentsIncludingCashClassifiedWithinOtherCurrentAssetsRelatedtoDiscontinuedOperations	684300000	USD
CY2017	us-gaap	Net Cash Provided By Used In Discontinued Operations NetCashProvidedByUsedInDiscontinuedOperations	-18800000	USD
CY2017	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	665500000	USD
CY2016Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	312800000	USD
CY2017Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	978300000	USD

Files In Submission

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$CLF
CLEVELAND-CLIFFS INC. Stock $clf

2019 Q4 Form 10-K Financial Statement

#000076406520000041 Filed on February 20, 2020

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$CLF CLEVELAND-CLIFFS INC. Stock $clf

2019 Q4 Form 10-K Financial Statement

#000076406520000041 Filed on February 20, 2020

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$CLF
CLEVELAND-CLIFFS INC. Stock $clf