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Commitments And Contingencies (Details) (USD $)
In Millions, unless otherwise specified |
3 Months Ended | 12 Months Ended | 3 Months Ended | 12 Months Ended | 3 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended | 3 Months Ended | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Mar. 31, 2012
Koolyanobbing [Member]
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Dec. 31, 2011
Koolyanobbing [Member]
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Dec. 31, 2010
Koolyanobbing [Member]
Mg
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Mar. 31, 2012
Koolyanobbing Rail Upgrade [Member]
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Dec. 31, 2011
Koolyanobbing Rail Upgrade [Member]
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Mar. 31, 2012
Koolynobbing Enhancements And Upgrades [Member]
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Mar. 31, 2012
Bloom Lake [Member]
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Mar. 31, 2012
Lower War Eagle [Member]
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Mar. 31, 2012
Empire [Member]
T
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Mar. 31, 2012
Empire And Tilden [Member]
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Dec. 31, 2012
Empire And Tilden [Member]
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Dec. 31, 2013
Empire And Tilden [Member]
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Mar. 31, 2012
Tilden [Member]
T
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Mar. 31, 2012
Oak Grove [Member]
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Dec. 31, 2011
Initial [Member]
Bloom Lake [Member]
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Dec. 31, 2011
Current [Member]
Bloom Lake [Member]
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| Related Party Transaction [Line Items] | ||||||||||||||||
| Capital investment required | $ 275 | $ 1,300 | ||||||||||||||
| Capital investment committed | 273 | 33 | 601 | 62 | 210 | 113 | ||||||||||
| Increase in production capacity, metric tons annually | 2,000,000 | |||||||||||||||
| Gross post-project production capacity, metric tons annually | 11,000,000 | 3,000,000 | ||||||||||||||
| Mine production capacity, metric tons per year | 8,000,000 | 16,000,000 | ||||||||||||||
| Capital Expenditures related to commitment | 225.0 | 17.0 | 235.0 | 52.0 | 160.0 | |||||||||||
| Capital investment, future payments | 16 | 16 | 366 | 10 | 39 | 11 | ||||||||||
| Capital investment commitment | $ 264 | |||||||||||||||