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Fixed Assets And Asset Retirement Obligations (Narrative) (Details) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Fixed Assets And Asset Retirement Obligations [Abstract]
Depreciation expense	$ 8,800,000	$ 5,800,000
Asset retirement obligation	$ 5,995,000

The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

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