Reclamation and Mine Closure (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Asset retirement obligation
Asset retirement obligation - Beginning	$ 35,197,000	$ 33,434,000	$ 34,457,000	$ 32,714,000
Accretion	758,000	742,000	1,500,000	1,466,000
Addition and changes in estimates	0	335,000	0	335,000
Settlements	(377,000)	(1,000)	(379,000)	(5,000)
Asset retirement obligation - March 31	35,578,000	34,510,000	35,578,000	34,510,000
Reclamation and Mine Closure (Textual) [Abstract]
Accrued reclamation liabilities	$ 600,000		$ 600,000		$ 900,000