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Asset Retirement Obligations (Changes In Asset Retirement Obligation Liability) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Asset Retirement Obligations [Abstract]
Asset retirement obligation as of beginning of period	$ 26,657	$ 24,003
Additional obligations	8,680	4,824
Accretion expense	2,246	2,598
Payments	(2,161)	(3,262)
Change in estimates	(647)	(1,236)
Foreign currency translation adjustments	(258)	(270)
Asset retirement obligation as of end of period	$ 34,517	$ 26,657

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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- Definition

Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability.

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