XML 114 R92.htm IDEA: XBRL DOCUMENT
v3.6.0.2

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Annual Contributions To The Pension Plans) (Details) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Defined Benefit Plan, Funded Percentage | 70.00% |
Company contributions | $ 1.1 | $ 3.5
Expected company contributions, next fiscal year | $ 4.1 |
Value of VEBA Trust Assets as a Percentage of the Funding Obligation | 0.9 |
Pension Benefits [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Company contributions | $ 1.2 | 35.7
Expected company contributions, next fiscal year | 24.5 |
Direct Payments [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Company contributions | 1.1 | 3.5
Expected company contributions, next fiscal year | 4.1 |
Veba Trust [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Company contributions | 0.0 | $ 0.0
Expected company contributions, next fiscal year | $ 0.0 |

X
- Definition Value of VEBA Trust Assets as a Percentage of the Funding Obligation that causes the funding obligation to be suspended. + References No definition available. + Details
Name: | clf_ValueOfVebaTrustAssetsAsPercentageOfFundingObligation
Namespace Prefix: | clf_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of contributions made by the employer to defined benefit plans. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(5)(ii) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Section 35 -Paragraph 123 -Subparagraph B -URI http://asc.fasb.org/extlink&oid=64937487&loc=d3e36068-114959 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Section 35 -Paragraph 63 -Subparagraph B -URI http://asc.fasb.org/extlink&oid=64937038&loc=d3e12551-114930 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(5)(iv)(01) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanContributionsByEmployer
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Plan assets of a defined benefit plan, as a percentage of projected benefit obligation. + References No definition available. + Details
Name: | us-gaap_DefinedBenefitPlanFundedPercentage
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_DefinedBenefitPlansAndOtherPostretirementBenefitPlansTableTextBlockLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlansEstimatedFutureEmployerContributionsInNextFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | clf_OtherBenefitsAxis=clf_DirectPaymentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | clf_OtherBenefitsAxis=clf_VebaTrustMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |