Line Of Credit Facility Revolving Loan Fair Value

No definition available.

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

- Details

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- Details

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- Definition

Fair value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion. Senior note holders are paid off in full before any payments are made to junior note holders.

+ References

No definition available.

+ Details

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

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. Amounts due from customers or clients for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, as well as any other amounts due from others, including related parties, which may be included in accounts receivable as categorized on the statement of financial position.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 14

-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13487-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.3)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 3

-Subparagraph a, b

-Article 5

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

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

- Definition

Interest rate stated in the contractual debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-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=6877327&loc=d3e13212-122682

+ Details

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Balance Type:	na
Period Type:	instant

- Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount borrowed under the credit facility as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

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

- Definition

+ References

No definition available.

+ Details

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

- Definition

The aggregate of amounts due from customers or clients more than one year from the balance sheet date, for goods or services that have been delivered or sold in the normal course of business and an amount representing an agreement for an unconditional promise by the maker to pay the Company (holder) a definite sum of money at a future date more than one year from the balance sheet date, reduced to their estimated net realizable fair value by an allowance established by the Company of the amount it deems uncertain of collection and net of any write-downs taken for collection uncertainty on the part of the holder, respectively.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-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=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 17

-Article 5

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Carrying amount of long-term debt, net of unamortized discount or premium, excluding amounts to be repaid within one year or the normal operating cycle, if longer (current maturities). 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/presentationRef

-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=6877327&loc=d3e13212-122682

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

An amount representing an agreement for an unconditional promise by the maker to pay the Company (holder) a definite sum of money within one year from the balance sheet date (or the normal operating cycle, whichever is longer), net of any write-downs taken for collection uncertainty on the part of the holder. Such amount may include accrued interest receivable in accordance with the terms of the debt. The debt also may contain provisions and related items including a discount or premium, payable on demand, secured, or unsecured, interest bearing or noninterest bearing, among a myriad of other features and characteristics. This amount does not include amounts related to receivables held-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 45

-Paragraph 9

-URI http://asc.fasb.org/extlink&oid=6375948&loc=d3e4531-111522

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6361293&loc=d3e6676-107765

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.3)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

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-Paragraph 3

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-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 43

-Section A

-Paragraph 4

-Chapter 3

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion. Senior note holders are paid off in full before any payments are made to junior note holders.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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Fair Value Of Financial Instruments (Carrying Value And Fair Value Of Financial Instruments Disclosure) (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 Carrying Value [Member]	Dec. 31, 2011 Carrying Value [Member]	Sep. 30, 2012 Carrying Value [Member] Customer Supplemental Payments [Member]	Dec. 31, 2011 Carrying Value [Member] Customer Supplemental Payments [Member]	Sep. 30, 2012 Carrying Value [Member] ArcelorMittal USA - Receivable [Member]	Dec. 31, 2011 Carrying Value [Member] ArcelorMittal USA - Receivable [Member]	Sep. 30, 2012 Carrying Value [Member] Other Credit Receivable [Member]	Dec. 31, 2011 Carrying Value [Member] Other Credit Receivable [Member]	Sep. 30, 2012 Fair Value [Member]	Dec. 31, 2011 Fair Value [Member]	Sep. 30, 2012 Fair Value [Member] Customer Supplemental Payments [Member]	Dec. 31, 2011 Fair Value [Member] Customer Supplemental Payments [Member]	Sep. 30, 2012 Fair Value [Member] ArcelorMittal USA - Receivable [Member]	Dec. 31, 2011 Fair Value [Member] ArcelorMittal USA - Receivable [Member]	Sep. 30, 2012 Fair Value [Member] Other Credit Receivable [Member]	Dec. 31, 2011 Fair Value [Member] Other Credit Receivable [Member]	Sep. 30, 2012 Term Loan - $1.25 Billion [Member] Carrying Value [Member]	Dec. 31, 2011 Term Loan - $1.25 Billion [Member] Carrying Value [Member]	Sep. 30, 2012 Term Loan - $1.25 Billion [Member] Fair Value [Member]	Dec. 31, 2011 Term Loan - $1.25 Billion [Member] Fair Value [Member]	Sep. 30, 2012 Senior Notes - $700 Million [Member] Carrying Value [Member]	Dec. 31, 2011 Senior Notes - $700 Million [Member] Carrying Value [Member]	Sep. 30, 2012 Senior Notes - $700 Million [Member] Fair Value [Member]	Dec. 31, 2011 Senior Notes - $700 Million [Member] Fair Value [Member]	Sep. 30, 2012 Senior Notes - $1.3 Billion [Member] Carrying Value [Member]	Dec. 31, 2011 Senior Notes - $1.3 Billion [Member] Carrying Value [Member]	Sep. 30, 2012 Senior Notes - $1.3 Billion [Member] Fair Value [Member]	Dec. 31, 2011 Senior Notes - $1.3 Billion [Member] Fair Value [Member]	Sep. 30, 2012 Senior Notes - $400 Million [Member]	Dec. 31, 2011 Senior Notes - $400 Million [Member] Carrying Value [Member]	Sep. 30, 2012 Senior Notes - $400 Million [Member] Fair Value [Member]	Dec. 31, 2011 Senior Notes - $400 Million [Member] Fair Value [Member]	Sep. 30, 2012 Senior Notes - $55 Million [Member] Carrying Value [Member]	Dec. 31, 2011 Senior Notes - $55 Million [Member] Carrying Value [Member]	Sep. 30, 2012 Senior Notes - $55 Million [Member] Fair Value [Member]	Dec. 31, 2011 Senior Notes - $55 Million [Member] Fair Value [Member]	Sep. 30, 2012 Revolving Loan [Member] Carrying Value [Member]	Dec. 31, 2011 Revolving Loan [Member] Carrying Value [Member]	Sep. 30, 2012 Revolving Loan [Member] Fair Value [Member]	Dec. 31, 2011 Revolving Loan [Member] Fair Value [Member]	Sep. 30, 2012 Empire [Member]	Dec. 31, 2011 Empire [Member]	Dec. 31, 2002 Empire [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	9.00%
Debt Instrument, Interest Rate, Stated Percentage	prime rate
Receivables:
Receivables, carrying value			$ 37.4	$ 58.8	$ 5.6	$ 22.3	$ 21.2	$ 26.5	$ 10.6	$ 10.0																																	$ 21.2	$ 26.5	$ 120.0
Notes, Loans and Financing Receivable, Net, Current																																											10.0	10.0
Receivables, fair value											39.3	61.5	5.2	20.8	23.5	30.7	10.6	10.0																									23.5	30.7
Long-term debt:
Term loan																			822.4	897.2	822.4	897.2
Senior notes																							699.4	699.3			1,289.3	1,289.2			398.2	398.0			55.0	325.0
Revolving loan																																							250.0	0
Senior notes																									772.7	726.4			1,576.3	1,399.4			467.4	448.8			62.8	348.7
Revolving loan																																									250.0	0
Total long-term debt	$ 3,514.3	$ 3,608.7	$ 3,514.3	$ 3,608.7							$ 3,951.6	$ 3,820.5