Sublimit for swingline loans

No definition available.

Name:	clf_CreditFacilitySublimitForSwinglineLoans
Namespace Prefix:	clf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line of Credit Facility, Maximum Borrowing Capacity, Exchange of Tranche B for Tranche A

+ References

No definition available.

+ Details

Name:	clf_LineOfCreditFacilityMaximumBorrowingCapacityExchangeOfTrancheBForTrancheA
Namespace Prefix:	clf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line of Credit Facility, Maximum Borrowing Capacity, Tranche A

+ References

No definition available.

+ Details

Name:	clf_LineOfCreditFacilityMaximumBorrowingCapacityTrancheA
Namespace Prefix:	clf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line of Credit Facility, Maximum Borrowing Capacity, Tranche A, Increase

+ References

No definition available.

+ Details

Name:	clf_LineOfCreditFacilityMaximumBorrowingCapacityTrancheAIncrease
Namespace Prefix:	clf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line of Credit Facility, Maximum Borrowing Capacity, Tranche B

+ References

No definition available.

+ Details

Name:	clf_LineOfCreditFacilityMaximumBorrowingCapacityTrancheB
Namespace Prefix:	clf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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_LineOfCreditFacilityLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- 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

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_LetterOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_LetterOfCreditMember
Namespace Prefix:
Data Type:	na
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Period Type:

DEBT AND CREDIT FACILITIES - ABL Facility (Details) - USD ($)	Dec. 31, 2021	Dec. 17, 2021	Dec. 09, 2020	Mar. 27, 2020	Mar. 13, 2020
ABL Facility \| Line of Credit
Line of Credit Facility [Line Items]
Credit facility, maximum borrowing capacity		$ 4,500,000,000			$ 2,000,000,000
Credit facility, sublimit for swingline loans					125,000,000
Filo tranche commitments			$ 150,000,000	$ 150,000,000
Increase in maximum borrowing capacity, tranche A		1,000,000,000	1,500,000,000
Maximum borrowing capacity, tranche A			$ 3,350,000,000
Exchange of Tranche B revolver commitments for Tranche A revolver commitments		$ 150,000,000
Letter of Credit \| Line of Credit
Line of Credit Facility [Line Items]
Credit facility, maximum borrowing capacity					$ 555,000,000
ABL Facility
Line of Credit Facility [Line Items]
Available borrowing base on ABL Facility	$ 4,500,000,000
Borrowings and Letter of credit obligations	(1,609,000,000)
Borrowing capacity available	2,716,000,000
Letter of Credit
Line of Credit Facility [Line Items]
Borrowings and Letter of credit obligations	$ (175,000,000)