Note 4. Environmental and Reclamation Activities (Detail) - Accrued Reclamation and Closure Cost Liability Activity (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Accruals for estimated costs	$ 7,869	$ 196,067	$ 5,980
Revision of estimated cash flows due to changes in reclamation plans			3,347
Receipt of settlement payment for shared reclamation costs incurred			3,150
Payment of reclamation obligations	(172,855)	(8,471)	(2,623)
Balance	318,797	131,201
Balance	$ 153,811	$ 318,797	$ 131,201