Cost Of Sales (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Cost of Revenue [Abstract]
Mining operations costs	$ 98,686	$ 87,387	$ 298,420	$ 258,487
Operations costs to metal inventory	(4,322)	1,310	(15,602)	851
Mining related depreciation and amortization	25,832	15,504	69,985	52,023
Accretion of asset retirement obligations	703	2,184	2,111	5,300
Total cost of sales	$ 120,899	$ 106,385	$ 354,914	$ 316,661