Segment Reporting (Details Textual) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting (Textual) [Abstract]
Total Revenue	$ 205,929	$ 230,593	$ 254,406	$ 204,564	$ 246,911	$ 343,575	$ 231,090	$ 199,624	$ 895,492	$ 1,021,200	$ 515,457
Silver [Member]
Segment Reporting (Textual) [Abstract]
Total Revenue									549,700	662,600	356,900
Gold [Member]
Segment Reporting (Textual) [Abstract]
Total Revenue									$ 345,800	$ 358,600	$ 158,500