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Derivative Instruments and Hedging Activities - Additional Information (Detail) (Commodity Contract, Cost of sales, USD $)
3 Months Ended 6 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Jun. 30, 2012
Jun. 30, 2011
Commodity Contract | Cost of sales
       
Derivative Instruments, Gain (Loss) [Line Items]        
Recognized gain (loss) in cost of sales on commodity contracts not designated as hedging instruments $ 291,000 $ (2,000) $ 835,000 $ 661,000