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Segment Reporting (Schedule Of Segment Reporting Information, By Segment) (Detail) (USD $)
In Millions, unless otherwise specified |
3 Months Ended | 9 Months Ended | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
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Sep. 30, 2012
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Sep. 30, 2011
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Sep. 30, 2012
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Sep. 30, 2011
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| Segment Reporting Information [Line Items] | ||||||||||
| Total revenues from product sales and services | $ 1,544.9 | $ 2,089.1 | $ 4,336.8 | $ 4,960.2 | ||||||
| Total revenues from product sales and services, percent | 100.00% | 100.00% | 100.00% | 100.00% | ||||||
| Sales margin | 198.3 | 843.1 | 933.6 | 2,130.8 | ||||||
| Other operating expense | (122.0) | (26.0) | (272.3) | (185.4) | ||||||
| Other expense | (43.9) | (54.7) | (134.7) | (61.0) | ||||||
| INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES AND EQUITY LOSS FROM VENTURES | 32.4 | 762.4 | 526.6 | 1,884.4 | ||||||
| Depreciation, depletion and amortization | 132.9 | 119.7 | 382.3 | 306.3 | ||||||
| Capital additions | 354.5 | 255.9 | 974.0 | [1] | 553.3 | [1] | ||||
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U.S. Iron Ore [Member]
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| Segment Reporting Information [Line Items] | ||||||||||
| Total revenues from product sales and services | 796.0 | 1,106.7 | 1,942.7 | 2,502.0 | ||||||
| Total revenues from product sales and services, percent | 52.00% | 52.00% | 45.00% | 49.00% | ||||||
| Sales margin | 255.9 | 481.3 | 708.9 | 1,283.7 | ||||||
| Depreciation, depletion and amortization | 24.9 | 23.0 | 71.9 | 62.5 | ||||||
| Capital additions | 19.6 | [1] | 28.5 | [1] | 82.5 | [1] | 115.8 | [1] | ||
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Eastern Canadian Iron Ore [Member]
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| Segment Reporting Information [Line Items] | ||||||||||
| Total revenues from product sales and services | 253.1 | 517.3 | 777.8 | 942.2 | ||||||
| Total revenues from product sales and services, percent | 16.00% | 24.00% | 18.00% | 18.00% | ||||||
| Sales margin | (40.5) | 191.0 | (43.0) | 293.5 | ||||||
| Depreciation, depletion and amortization | 41.7 | 43.2 | 118.2 | 84.5 | ||||||
| Capital additions | 285.5 | [1] | 103.3 | [1] | 593.4 | [1] | 167.5 | [1] | ||
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Asia Pacific Iron Ore [Member]
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| Segment Reporting Information [Line Items] | ||||||||||
| Total revenues from product sales and services | 254.2 | 400.1 | 975.3 | 1,127.1 | ||||||
| Total revenues from product sales and services, percent | 16.00% | 19.00% | 22.00% | 22.00% | ||||||
| Sales margin | (15.8) | 214.6 | 256.1 | 615.4 | ||||||
| Depreciation, depletion and amortization | 40.2 | 25.4 | 110.0 | 74.3 | ||||||
| Capital additions | 5.8 | [1] | 57.3 | [1] | 132.0 | [1] | 140.6 | [1] | ||
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North American Coal [Member]
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| Segment Reporting Information [Line Items] | ||||||||||
| Total revenues from product sales and services | 241.8 | 64.0 | 640.9 | 388.7 | ||||||
| Total revenues from product sales and services, percent | 16.00% | 3.00% | 15.00% | 8.00% | ||||||
| Sales margin | (1.3) | (42.7) | 3.8 | (60.4) | ||||||
| Depreciation, depletion and amortization | 25.1 | 19.7 | 69.5 | 62.1 | ||||||
| Capital additions | 33.3 | [1] | 60.3 | [1] | 105.1 | [1] | 116.3 | [1] | ||
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All Other Segments [Member]
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| Segment Reporting Information [Line Items] | ||||||||||
| Total revenues from product sales and services | (0.2) | 1.0 | 0.1 | 0.2 | ||||||
| Total revenues from product sales and services, percent | 0.00% | 2.00% | 0.00% | 3.00% | ||||||
| Sales margin | 0 | (1.1) | 7.8 | (1.4) | ||||||
| Depreciation, depletion and amortization | 1.0 | 8.4 | 12.7 | 22.9 | ||||||
| Capital additions | $ 10.3 | [1] | $ 6.5 | [1] | $ 61.0 | [1] | $ 13.1 | [1] | ||
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