Derivative Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2011
Effect of derivative instruments on the statement of operations
Amount of Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	$ (380)
Amount Reclassified from Accumulated OCI into Income	5,610
Operating Costs [Member]
Effect of derivative instruments on the statement of operations
Amount Reclassified from Accumulated OCI into Income	157
Interest expense, net of amounts capitalized [Member]
Effect of derivative instruments on the statement of operations
Amount Reclassified from Accumulated OCI into Income	5,453
Interest rate swaps [Member]
Effect of derivative instruments on the statement of operations
Amount of Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	(286)
Natural gas swaps [Member]
Effect of derivative instruments on the statement of operations
Amount of Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	$ (94)

Pre tax reclassification adjustment for accumulated gains and losses from derivative instrument designated and qualifying as the effective portion of cash flow hedges included in accumulated comprehensive income that was realized in net income during the period. A cash flow hedge is a hedge of the exposure to variability in the cash flows of a recognized asset or liability or a forecasted transaction that is attributable to a particular risk.

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-Glossary Reclassification Adjustments

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+ Details

- Definition

Pre tax change in accumulated gains and losses from derivative instrument designated and qualifying as the effective portion of cash flow hedges. A cash flow hedge is a hedge of the exposure to variability in the cash flows of a recognized asset or liability or a forecasted transaction that is attributable to a particular risk. Includes an entity's share of an equity investee's Increase or Decrease in deferred hedging gains or losses.

+ References

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+ Details