Note 4. Environmental and Reclamation Activities (Detail) (USD $)	1 Months Ended					3 Months Ended		12 Months Ended
	Oct. 31, 2011	Jun. 30, 2011	Mar. 31, 2010	Jan. 31, 2010	Dec. 31, 2009	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Increase Decrease In Accrued Reclamation							$ 193,200,000
Liabilities Subject to Compromise, Provision for Expected and Allowed Claims							262,200,000		262,200,000
Other Accrued Liabilities							264,400,000		264,400,000
Payments for Legal Settlements	168,000,000					1
Surety Bonds	96,400,000						96,400,000		96,400,000
Remaining Payment Obligation						95,400,000		95,400,000
Incurred Response Costs			5,300,000	91,000,000
Estimated Response Costs		4,500,000	2.7
Proceeds from Other Debt					3,300,000
								(172,855,000)	(8,666,000)	1,540,000
Increase (Decrease) in Accounts Receivable								(16,531,000)	9,404,000	18,117,000
Accrued Reclamation And Closure Costs Total					131,201,000	153,811,000	318,797,000	153,811,000	318,797,000	131,201,000
ASARCO Claim Amount [Member]
					3,200,000
Maximum Potentail Liability [Member]
Estimated Response Costs			6,800,000
ASARCO Claim Amount [Member]
Increase (Decrease) in Accounts Receivable					100,000
Minimum Risk Free Interest Rate [Member]
Risk Free Interest Rate							6.00%		6.00%
Maximum Risk Free Interst Rate [Member]
Risk Free Interest Rate							7.00%		7.00%
Minimum Potentail Liability [Member]
Estimated Response Costs			$ 2.7