Segment Reporting (Details Textual) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Segment Reporting (Textual) [Abstract]
Total Revenue	$ 254,406	$ 231,090	$ 458,970	$ 430,714
Silver [Member]
Segment Reporting (Textual) [Abstract]
Total Revenue	160,700	158,800	299,900	271,300
Gold [Member]
Segment Reporting (Textual) [Abstract]
Total Revenue	$ 93,700	$ 72,300	$ 159,000	$ 159,400