ÐÇ¿Õ´«Ã½

Annual report pursuant to Section 13 and 15(d)

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Narrative) (Details)

v3.3.1.900
BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Narrative) (Details)
T in Millions
12 Months Ended
Dec. 31, 2015
USD ($)
Facility
T
Dec. 31, 2014
USD ($)
T
Dec. 31, 2013
USD ($)
shares
Jul. 10, 2012
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Deferred Tax Assets, Gross, Current Ìý $ 23,700,000 Ìý Ìý
Tangible Asset Impairment Charges Ìý 537,800,000 Ìý Ìý
Inventory Valuation Reserves $ 31,800,000 16,000,000 Ìý Ìý
Trading Day Window Determining Number of Common Shares Issuable on Conversion 20 Ìý Ìý Ìý
Depositary Share Interest in a Share of 7% Series A Mandatory Convertible Preferred Stock, Class A 0.025 Ìý Ìý Ìý
Current Fiscal Year End Date --12-31 Ìý Ìý Ìý
Goodwill $ 2,000,000 2,000,000 $ 74,500,000 Ìý
Freight and venture partners' cost reimbursements 180,900,000 278,000,000 259,000,000 Ìý
Allowance for Doubtful Accounts Receivable 7,100,000 0 Ìý Ìý
Provision for Doubtful Accounts $ 7,100,000 Ìý 0.0 Ìý
Derivative, Policy, Percentage of Amount Permitted to be Hedged 75.00% Ìý Ìý Ìý
Derivative, Policy, Minimum Percentage of Amount Permitted to be Hedged for Derivatives with Periods of up to Twelve Months 40.00% Ìý Ìý Ìý
Derivative, Policy, Minimum Percentage of Amount Permitted to be Hedged for Derivatives with Periods of up to Fifteen Months 10.00% Ìý Ìý Ìý
Discontinued Operation, Tax Effect of Discontinued Operation $ (6,000,000) (1,216,000,000) (184,500,000) Ìý
Asset Impairment Charges 3,300,000 635,500,000 14,300,000 Ìý
Goodwill, Impairment Loss 0 73,500,000 Ìý Ìý
Impairment of Intangible Assets (Excluding Goodwill) Ìý 13,800,000 Ìý Ìý
Deferred Tax Liabilities, Gross, Current Ìý 4,000,000 Ìý Ìý
Unamortized Debt Issuance Expense $ 29,100,000 16,800,000 Ìý Ìý
Amapa [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Equity Method Investment, Other than Temporary Impairment Ìý Ìý 67,600,000 Ìý
U.S. Iron Ore [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Number Of Mines | Facility 5 Ìý Ìý Ìý
Goodwill $ 2,000,000 2,000,000 2,000,000 Ìý
Freight and venture partners' cost reimbursements $ 157,300,000 $ 271,000,000 259,500,000 Ìý
Quantity Of Finished Goods | T 1.3 1.4 Ìý Ìý
Goodwill, Impairment Loss $ 0 $ 0 Ìý Ìý
Asia Pacific [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Freight and venture partners' cost reimbursements $ 23,600,000 6,900,000 Ìý Ìý
Asia Pacific Iron Ore [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Number Of Mines | Facility 1 Ìý Ìý Ìý
Goodwill $ 0 0 $ 72,500,000 Ìý
Goodwill, Impairment Loss $ 0 73,500,000 Ìý Ìý
Sonoma [Member] | Asia Pacific Coal [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Ownership Interest Ìý Ìý Ìý 45.00%
Empire [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Noncontrolling Interest, Ownership Percentage by Parent 79.00% Ìý Ìý Ìý
Bloom Lake [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Noncontrolling Interest, Ownership Percentage by Parent Ìý Ìý 82.80% Ìý
Investments in Ventures [Member] | Amapa [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Ownership interest, equity method investment Ìý Ìý 30.00% Ìý
Low Volatile Metallurgical Coal Mines [Member] | North American Coal [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Number Of Mines | Facility 2 Ìý Ìý Ìý
Take or Pay Contracts [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Deferred Revenue Ìý 29,300,000 Ìý Ìý
Customer Supplemental Payments [Member] | U.S. Iron Ore [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Deferred Revenue $ 89,900,000 102,800,000 Ìý Ìý
Deferred Revenue, Current 12,800,000 12,800,000 Ìý Ìý
Deferred Revenue, Noncurrent $ 77,100,000 90,000,000 Ìý Ìý
Wisco [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Increase in Subsidiary or Equity Method Investee Percentage Ownership Acquired Ìý Ìý 7.80% Ìý
Units Issued by CQIM to Bloom Lake for Acquisition of Noncontrolling Interest | shares Ìý Ìý 457,556 Ìý
Subsidiary Or Equity Method Investee Percentage Ownership Acquired Ìý Ìý 17.152% Ìý
Increase/Decrease in Equity for WISCO/Bloom Lake through Acquisition of Noncontrolling Interest Ìý Ìý $ 314,800,000 Ìý
Bloom Lake [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Increase to Cliffs' Shareholders Equity through Acquisition of Noncontrolling Interest Ìý 314,800,000 Ìý Ìý
Minimum [Member] | Other Machinery and Equipment [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Property, Plant and Equipment, Useful Life 10 years Ìý Ìý Ìý
Minimum [Member] | Electric Power Facilities [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Property, Plant and Equipment, Useful Life 10 years Ìý Ìý Ìý
Minimum [Member] | Land Improvements [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Property, Plant and Equipment, Useful Life 20 years Ìý Ìý Ìý
Minimum [Member] | Equipment [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Property, Plant and Equipment, Useful Life 3 years Ìý Ìý Ìý
Maximum [Member] | Other Machinery and Equipment [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Property, Plant and Equipment, Useful Life 45 years Ìý Ìý Ìý
Maximum [Member] | Electric Power Facilities [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Property, Plant and Equipment, Useful Life 45 years Ìý Ìý Ìý
Maximum [Member] | Land Improvements [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Property, Plant and Equipment, Useful Life 45 years Ìý Ìý Ìý
Maximum [Member] | Equipment [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Property, Plant and Equipment, Useful Life 20 years Ìý Ìý Ìý
Short-term intercompany loan [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Foreign Currency Transaction Gain (Loss), before Tax $ 11,500,000 19,700,000 33,000,000 Ìý
Transaction Gains and Losses Resulting from Remeasurement [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Foreign Currency Transaction Gain (Loss), before Tax 16,300,000 29,000,000 53,200,000 Ìý
Cash and Cash Equivalents [Member] Ìý Ìý Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý Ìý Ìý
Foreign Currency Transaction Gain (Loss), before Tax $ 1,500,000 $ 10,600,000 $ 20,400,000 Ìý