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Note 13. Asset Retirement Obligations (Detail) - Reconciliation of Retirement Asset Obligations (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011
Balance, January 1	$ 37,643	$ 36,397
Changes in obligations due to changes in reclamation plans		387
Accretion expense	562	1,119
Payment of reclamation obligations	(170)	(260)
Balance, end of period	$ 38,035	$ 37,643

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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