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Derivatives, Hedges, Financial Instruments and Carbon Credits - Assets and Liabilities Measured at Fair Value on Recurring Basis (Parenthetical) (Detail)
$ in Thousands
Dec. 31, 2015
USD ($)
Recurring [Member] | Commodities Contracts [Member]  
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]  
Commodities contracts $ 195