XML 88 R68.htm IDEA: XBRL DOCUMENT
v3.21.1

DEBT AND CREDIT FACILITIES - Schedule Of Long-Term Debt (Details) - USD ($) $ in Millions | Mar. 31, 2021 | Feb. 17, 2021 | Dec. 31, 2020
--- | --- | --- | ---
Debt Instrument [Line Items] |  |  |
Total Principal Amount | $ 5,893 |  |
Long-term Debt |  |  | $ 5,424
Long-term Debt, Current Maturities |  |  | 34
Total long-term debt | 5,734 |  | $ 5,390
ABC Facility |  |  |
Debt Instrument [Line Items] |  |  |
Long-term Line of Credit | 1,630 |  |
Maximum borrowing capacity | 3,500 |  |
Cleveland-Cliffs Inc. |  |  |
Debt Instrument [Line Items] |  |  |
Annual Effective Interest Rate |  |  | 3.25%
Cleveland-Cliffs Inc. | EDC Revolving Facilities - outstanding balance |  |  |
Debt Instrument [Line Items] |  |  |
Long-term Line of Credit | 53 |  | $ 18
Maximum borrowing capacity | 80 |  | $ 40
Cleveland-Cliffs Inc. | ABC Facility |  |  |
Debt Instrument [Line Items] |  |  |
Annual Effective Interest Rate |  |  | 2.15%
Maximum borrowing capacity | $ 3,500 |  | $ 3,500
Cleveland-Cliffs Inc. | 9.875% 2025 Senior Secured Notes |  |  |
Debt Instrument [Line Items] |  |  |
Stated interest rate | 9.875% |  | 9.875%
Annual Effective Interest Rate | 10.57% |  | 10.57%
Total Principal Amount | $ 633 |  | $ 955
Unamortized Debt Issuance Costs | (5) |  | (8)
Unamortized (Discounts) | (16) |  | (25)
Long-term Debt | $ 612 |  | $ 922
Cleveland-Cliffs Inc. | 6.75% 2026 Senior Secured Notes |  |  |
Debt Instrument [Line Items] |  |  |
Stated interest rate | 6.75% |  | 6.75%
Annual Effective Interest Rate | 6.99% |  | 6.99%
Total Principal Amount | $ 845 |  | $ 845
Unamortized Debt Issuance Costs | (19) |  | (20)
Unamortized (Discounts) | (8) |  | (9)
Long-term Debt | $ 818 |  | $ 816
Cleveland-Cliffs Inc. | 1.50% 2025 Convertible Senior Notes |  |  |
Debt Instrument [Line Items] |  |  |
Stated interest rate | 1.50% |  | 1.50%
Annual Effective Interest Rate | 6.26% |  | 6.26%
Total Principal Amount | $ 296 |  | $ 296
Unamortized Debt Issuance Costs | (3) |  | (4)
Unamortized (Discounts) | (47) |  | (49)
Long-term Debt | $ 246 |  | $ 243
Cleveland-Cliffs Inc. | 5.75% 2025 Senior Notes |  |  |
Debt Instrument [Line Items] |  |  |
Stated interest rate | 5.75% |  | 5.75%
Annual Effective Interest Rate | 6.01% |  | 6.01%
Total Principal Amount | $ 396 |  | $ 396
Unamortized Debt Issuance Costs | (2) |  | (3)
Unamortized (Discounts) | (4) |  | (4)
Long-term Debt | $ 390 |  | $ 389
Cleveland-Cliffs Inc. | 7.00% 2027 Senior Notes |  |  |
Debt Instrument [Line Items] |  |  |
Stated interest rate | 7.00% |  | 7.00%
Annual Effective Interest Rate | 9.24% |  | 9.24%
Total Principal Amount | $ 73 |  | $ 73
Unamortized Debt Issuance Costs | 0 |  | 0
Unamortized (Discounts) | (7) |  | (8)
Long-term Debt | $ 66 |  | $ 65
Cleveland-Cliffs Inc. | 5.875% 2027 Senior Notes |  |  |
Debt Instrument [Line Items] |  |  |
Stated interest rate | 5.875% |  | 5.875%
Annual Effective Interest Rate | 6.49% |  | 6.49%
Total Principal Amount | $ 556 |  | $ 556
Unamortized Debt Issuance Costs | (4) |  | (4)
Unamortized (Discounts) | (17) |  | (18)
Long-term Debt | $ 535 |  | $ 534
Cleveland-Cliffs Inc. | 4.625% 2029 Senior Notes |  |  |
Debt Instrument [Line Items] |  |  |
Stated interest rate | 4.625% |  |
Annual Effective Interest Rate | 4.63% |  |
Total Principal Amount | $ 500 | $ 500 |
Unamortized Debt Issuance Costs | (9) |  |
Unamortized (Discounts) | 0 |  |
Long-term Debt | $ 491 |  |
Cleveland-Cliffs Inc. | 4.875% 2031 Senior Notes |  |  |
Debt Instrument [Line Items] |  |  |
Stated interest rate | 4.875% |  |
Annual Effective Interest Rate | 4.88% |  |
Total Principal Amount | $ 500 | $ 500 |
Unamortized Debt Issuance Costs | (9) |  |
Unamortized (Discounts) | 0 |  |
Long-term Debt | $ 491 |  |
Cleveland-Cliffs Inc. | 6.25% 2040 Senior Notes |  |  |
Debt Instrument [Line Items] |  |  |
Stated interest rate | 6.25% |  | 6.25%
Annual Effective Interest Rate | 6.34% |  | 6.34%
Total Principal Amount | $ 263 |  | $ 263
Unamortized Debt Issuance Costs | (2) |  | (2)
Unamortized (Discounts) | (3) |  | (3)
Long-term Debt | $ 258 |  | 258
Cleveland-Cliffs Inc. | ABC Facility |  |  |
Debt Instrument [Line Items] |  |  |
Annual Effective Interest Rate | 2.14% |  |
Long-term Line of Credit | $ 1,630 |  | $ 1,510
Cleveland-Cliffs Inc. | 4.875% 2024 Senior Notes |  |  |
Debt Instrument [Line Items] |  |  |
Stated interest rate |  |  | 4.875%
Annual Effective Interest Rate |  |  | 5.00%
Total Principal Amount |  |  | $ 395
Unamortized Debt Issuance Costs |  |  | (3)
Unamortized (Discounts) |  |  | (1)
Long-term Debt |  |  | $ 391
Cleveland-Cliffs Inc. | 6.375% 2025 Senior Notes |  |  |
Debt Instrument [Line Items] |  |  |
Stated interest rate |  |  | 6.375%
Annual Effective Interest Rate |  |  | 8.11%
Total Principal Amount |  |  | $ 64
Unamortized Debt Issuance Costs |  |  | 0
Unamortized (Discounts) |  |  | (4)
Long-term Debt |  |  | 60
AK Steel | Industrial Revenue Bonds |  |  |
Debt Instrument [Line Items] |  |  |
Total Principal Amount |  |  | 92
Unamortized Debt Issuance Costs |  |  | 0
Unamortized Premiums |  |  | 2
Long-term Debt |  |  | $ 94
AK Steel | 7.00% 2027 AK Senior Notes |  |  |
Debt Instrument [Line Items] |  |  |
Stated interest rate | 7.00% |  | 7.00%
Annual Effective Interest Rate | 9.24% |  | 9.24%
Total Principal Amount | $ 56 |  | $ 56
Unamortized Debt Issuance Costs | 0 |  | 0
Unamortized (Discounts) | (6) |  | (6)
Long-term Debt | 50 |  | $ 50
AK Steel | Industrial Revenue Bonds |  |  |
Debt Instrument [Line Items] |  |  |
Total Principal Amount | 92 |  |
Unamortized Debt Issuance Costs | 0 |  |
Unamortized Premiums | 2 |  |
Long-term Debt | $ 94 |  |
AK Steel | 7.625% 2021 AK Senior Notes |  |  |
Debt Instrument [Line Items] |  |  |
Stated interest rate |  |  | 7.625%
Annual Effective Interest Rate |  |  | 7.33%
Total Principal Amount |  |  | $ 34
Unamortized Debt Issuance Costs |  |  | 0
Unamortized (Discounts) |  |  | 0
Long-term Debt |  |  | $ 34
AK Steel | 7.50% Senior Secured Notes due July 2023 |  |  |
Debt Instrument [Line Items] |  |  |
Stated interest rate |  |  | 7.50%
Annual Effective Interest Rate |  |  | 6.17%
Total Principal Amount |  |  | $ 13
Unamortized Debt Issuance Costs |  |  | 0
Unamortized (Discounts) |  |  | 0
Long-term Debt |  |  | $ 13
AK Steel | 6.375% 2025 AK Senior Notes |  |  |
Debt Instrument [Line Items] |  |  |
Stated interest rate |  |  | 6.375%
Annual Effective Interest Rate |  |  | 8.11%
Total Principal Amount |  |  | $ 29
Unamortized Debt Issuance Costs |  |  | 0
Unamortized (Discounts) |  |  | (2)
Long-term Debt |  |  | $ 27

X
- Definition Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6031897-161870 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(16)) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 + Details
Name: | us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6036836-161870 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DebtInstrumentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount, after accumulated amortization, of debt discount. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28541-108399 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400 + Details
Name: | us-gaap_DebtInstrumentUnamortizedDiscount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, after accumulated amortization, of debt premium. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28541-108399 + Details
Name: | us-gaap_DebtInstrumentUnamortizedPremium
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(16)) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 + Details
Name: | us-gaap_LineOfCredit
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6031897-161870 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(16)) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_LongTermDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19,20) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_LongTermDebtCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_LongTermDebtNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.17) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_UnamortizedDebtIssuanceExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_DebtInstrumentAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=clf_ClevelandCliffsInc.Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=clf_EDCRevolvingCreditFacilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=clf_A98752025SeniorSecuredNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=clf_A6.752026SeniorSecuredNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=clf_A1.502025ConvertibleSeniorNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=clf_A5.752025SeniorNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=clf_A7.002027SeniorNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=clf_A5.8752027SeniorNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=clf_A46252029SeniorNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=clf_A48752031SeniorNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=clf_A6.252040SeniorNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=clf_A4.8752024SeniorSecuredNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=clf_A6.3752025SeniorNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=clf_AKSteelMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=clf_IndustrialRevenueBondsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=clf_A7002027AKSeniorNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=clf_IndustrialRevenueBondsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=clf_A7.6252021AKSeniorNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=clf_A7.502023AKSeniorNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=clf_A63752025AKSeniorNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |