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Asset Retirement Obligation (Details Textual) (USD $)	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2010	Dec. 31, 2008
Asset Retirement Obligation (Textual) [Abstract]
Fair value of asset retirement obligations related to the legal requirements					$ 11,500,000
Asset retirement obligation	9,081,000	9,679,000	9,087,000	9,717,000
Other current liabilities [Member]
Asset Retirement Obligation (Textual) [Abstract]
Asset retirement obligation	3,100,000
Other long-term liabilities [Member]
Asset Retirement Obligation (Textual) [Abstract]
Asset retirement obligation	$ 6,000,000

The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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