Reclamation (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Asset retirement obligation
Asset retirement obligation - Beginning	$ 58,460,000	$ 35,197,000	$ 57,454,000	$ 34,457,000
Accretion	1,435,000	758,000	2,752,000	1,500,000
Settlements	(100,000)	(377,000)	(411,000)	(379,000)
Asset retirement obligation - Ending	59,795,000	35,578,000	59,795,000	35,578,000
Reclamation and Mine Closure (Textual) [Abstract]
Accrued reclamation liabilities	$ 700,000		$ 700,000		$ 1,000,000