Related Party Transactions - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified |
3 Months Ended | 9 Months Ended | |||
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Sep. 30, 2013
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Sep. 30, 2012
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Sep. 30, 2013
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Sep. 30, 2012
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Dec. 31, 2012
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Related Party Transaction [Line Items] | |||||
Net sales to related parties | $ 275 | $ 342 | $ 863 | $ 1,003 | |
Accounts payable to related parties | 93 | 93 | 78 | ||
Outside processing services
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Related Party Transaction [Line Items] | |||||
Purchases from related parties | 18 | 16 | 53 | 44 | |
Taconite pellets
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Related Party Transaction [Line Items] | |||||
Purchases from related parties | 63 | 84 | 180 | 204 | |
PRO-TEC Coating Company
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Related Party Transaction [Line Items] | |||||
Accounts payable to related parties | 89 | 89 | 75 | ||
Other equity investees
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Related Party Transaction [Line Items] | |||||
Accounts payable to related parties | $ 4 | $ 4 | $ 3 |