Derivative Instruments (Outstanding Derivative Contracts That Were Entered Into To Hedge Forecasted Transactions) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011 Mmbtu	Dec. 31, 2010 Mmbtu	Dec. 31, 2009 Mmbtu
Natural Gas Contracts [Member]
Derivative [Line Items]
Outstanding derivative contracts that were entered into to hedge forecasted transactions	700,000	985,000	1,070,000
Foreign Exchange Contracts [Member]
Derivative [Line Items]
Outstanding derivative contracts that were entered into to hedge forecasted transactions	35,304	20,727	14,552
Currency Swap [Member]
Derivative [Line Items]
Outstanding derivative contracts that were entered into to hedge forecasted transactions			3,646