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Fixed Assets And Asset Retirement Obligations (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Fixed Assets And Asset Retirement Obligations [Abstract]
Depreciation expense	$ 27.3	$ 22.5	$ 25.2

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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