Derivatives, Hedges, Financial Instruments and Carbon Credits (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Total net gains (losses) included in earnings:
Derivative instruments and carbon credits, gains and losses recognized in earnings	$ 46	$ (449)
Derivative instruments and carbon credits change in unrealized gains and losses recognized in earnings	412	(12)
Cost of Sales [Member] | Commodities Contracts [Member]
Total net gains (losses) included in earnings:
Derivative instruments and carbon credits, gains and losses recognized in earnings	142	(151)
Derivative instruments and carbon credits change in unrealized gains and losses recognized in earnings	142	(82)
Cost of Sales [Member] | Foreign Exchange Contracts [Member]
Total net gains (losses) included in earnings:
Derivative instruments and carbon credits, gains and losses recognized in earnings		40
Derivative instruments and carbon credits change in unrealized gains and losses recognized in earnings		18
Other Income [Member] | Carbon Credits [Member]
Total net gains (losses) included in earnings:
Derivative instruments and carbon credits, gains and losses recognized in earnings		40
Other Expense [Member] | Contractual obligations relating to carbon credits [Member]
Total net gains (losses) included in earnings:
Derivative instruments and carbon credits, gains and losses recognized in earnings		(40)
Interest Expense [Member] | Interest Rate Contracts [Member]
Total net gains (losses) included in earnings:
Derivative instruments and carbon credits, gains and losses recognized in earnings	(96)	(338)
Derivative instruments and carbon credits change in unrealized gains and losses recognized in earnings	$ 270	$ 52