Derivatives and Financial Instruments (Narrative) (Detail)
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0 Months Ended | 9 Months Ended | |
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Sep. 30, 2012
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Dec. 31, 2011
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Sep. 30, 2012
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Derivative [Line Items] | |||
Percentage of derivative contract volume expiring within next 12 months | 99.00% | 99.00% | |
Payment terms of receivables | 30 days or less |