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Quarterly Results of Operations (Narrative) (Details) (USD $)
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3 Months Ended | 9 Months Ended | 12 Months Ended | 9 Months Ended | 3 Months Ended | 6 Months Ended | 9 Months Ended | 3 Months Ended | 9 Months Ended | 3 Months Ended | 12 Months Ended | 3 Months Ended | 6 Months Ended | 9 Months Ended | ||||||||||||||||
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Dec. 31, 2011
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Sep. 30, 2011
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Jun. 30, 2011
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Mar. 31, 2011
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Dec. 31, 2010
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Sep. 30, 2010
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Jun. 30, 2010
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Mar. 31, 2010
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Sep. 30, 2011
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Dec. 31, 2011
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Dec. 31, 2010
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Dec. 31, 2009
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Dec. 31, 2010
Freewest [Member]
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Jan. 27, 2010
Freewest [Member]
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Sep. 30, 2011
Arcelor Mittal [Member]
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Jun. 30, 2011
Empire [Member]
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Mar. 31, 2011
Empire [Member]
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Jun. 30, 2011
Empire [Member]
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Sep. 30, 2011
Empire [Member]
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Dec. 31, 2002
Empire [Member]
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Dec. 31, 2001
Empire [Member]
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Dec. 31, 2011
CLCC [Member]
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Feb. 01, 2010
Wabush [Member]
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Sep. 30, 2011
Consolidated Thompson [Member]
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Sep. 30, 2011
Scenario, Adjustment [Member]
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Mar. 31, 2010
Scenario, Adjustment [Member]
Wabush [Member]
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Dec. 31, 2010
Scenario, Adjustment [Member]
Wabush [Member]
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Sep. 30, 2011
Scenario, Adjustment [Member]
Consolidated Thompson [Member]
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Jun. 30, 2011
Scenario, Adjustment [Member]
Consolidated Thompson [Member]
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Sep. 30, 2011
Scenario, Adjustment [Member]
Consolidated Thompson [Member]
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| Related Party Transaction [Line Items] | ||||||||||||||||||||||||||||||
| Fair value | $ 27,400,000 | $ 38,000,000 | ||||||||||||||||||||||||||||
| Interest Percentage | 12.40% | 46.70% | 46.70% | 26.80% | ||||||||||||||||||||||||||
| Empire's ownership percentage | 21.00% | |||||||||||||||||||||||||||||
| Percent interest acquired | 79.00% | 79.00% | ||||||||||||||||||||||||||||
| Gain on acquisition of controlling interests | 38,600,000 | 40,700,000 | 13,600,000 | 25,000,000 | ||||||||||||||||||||||||||
| Retained earnings | (4,424,300,000) | 67,900,000 | (2,924,100,000) | 67,900,000 | (4,424,300,000) | (2,924,100,000) | 16,100,000 | |||||||||||||||||||||||
| Minority Interest | 1,254,700,000 | 84,000,000 | (7,200,000) | 84,000,000 | 1,254,700,000 | (7,200,000) | ||||||||||||||||||||||||
| Prior period reclassification adjustment | 54,100,000 | 103,000,000 | 46,000,000 | |||||||||||||||||||||||||||
| Reduction in earnings per share basic | $ 0.47 | $ 0.49 | ||||||||||||||||||||||||||||
| Reduction in earnings per share diluted | $ 0.48 | |||||||||||||||||||||||||||||
| Goodwill, Impairment Loss | 27,800,000 | 27,800,000 | ||||||||||||||||||||||||||||
| INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES AND EQUITY LOSS FROM VENTURES | 16,100,000 | 2,241,500,000 | 1,303,000,000 | 296,500,000 | 22,000,000 | 2,000,000 | 500,000 | 2,500,000 | ||||||||||||||||||||||
| Net income (loss) attributable to Cliffs shareholders | 185,400,000 | 601,200,000 | 409,100,000 | 423,400,000 | 384,100,000 | 297,600,000 | 260,800,000 | 77,400,000 | 1,619,100,000 | 1,019,900,000 | 205,100,000 | (30,400,000) | (37,500,000) | (67,900,000) | 13,100,000 | 16,100,000 | 11,700,000 | 1,400,000 | ||||||||||||
| Decrease in basic and diluted earnings per share | 0.12 | |||||||||||||||||||||||||||||
| Increase in basic and diluted earnings per share | $ 0.08 | $ 0.09 | $ 0.01 | $ 0.09 | ||||||||||||||||||||||||||