Reclamation and Mine Closure (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Asset retirement obligation
Asset retirement obligation - Beginning	$ 33,434,000	$ 27,908,000	$ 32,714,000	$ 27,302,000
Accretion	742,000	654,000	1,466,000	1,290,000
Addition and changes in estimates	335,000	0	335,000	0
Settlements	(1,000)	(5,000)	(5,000)	(35,000)
Asset retirement obligation - March 31	34,510,000	28,557,000	34,510,000	28,557,000
Reclamation and Mine Closure (Textual) [Abstract]
Accrued reclamation liabilities	$ 800,000		$ 800,000		$ 1,000,000