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Schedule Of Outstanding Forward Contracts That Were Entered Into Hedge Forecasted Transactions (Detail)	Jun. 30, 2012 mwh	Dec. 31, 2011 mwh
Derivative Instruments, Gain (Loss) [Line Items]
Natural gas (million British thermal units)	17,780,000
Energy Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Energy contracts (electricity-megawatt hours)	100,578,295	100,578,295
Aluminum Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Aluminum contracts (kmt)	1,190	1,294

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- Definition

Outstanding Forward Contracts Entered Into As Hedge Forecasted Transactions Measured In British Thermal Units

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- Definition

Outstanding forward contracts entered into as hedge forecasted transactions measured in mega watt hours.

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- Definition

Outstanding forward contracts entered into as hedging forecasted transactions measured in kilo metric ton.

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