Derivatives, Hedges, Financial Instruments and Carbon Credits - Net Gains (Losses) Included in Operating Results and Statement of Operations Classifications (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Total net gain (losses) included in operating results	$ (2,513)	$ (2,102)
Cost of Sales [Member] | Commodities Contracts [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gain (losses) included in operating results	(17)	(1,978)
Cost of Sales [Member] | Foreign Exchange Contracts [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gain (losses) included in operating results	13	(93)
Other Income [Member] | Carbon Credits [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gain (losses) included in operating results	60	(30)
Other Expense [Member] | Contractual Obligations Relating to Carbon Credits [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gain (losses) included in operating results	(60)	30
Non-operating Other Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Non-operating other expense - embedded derivative	$ (2,509)
Interest Expense [Member] | Interest Rate Contracts [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gain (losses) included in operating results		$ (31)