Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Dec. 31, 2012 Silver ounces received from Mandalay [Member]	Mar. 31, 2013 Royalty obligation embedded derivative [Member]	Dec. 31, 2012 Royalty obligation embedded derivative [Member]	Mar. 31, 2013 Put and call options [Member]	Dec. 31, 2012 Put and call options [Member]	Mar. 31, 2013 Other derivative instrument [Member]	Mar. 31, 2013 Short-term Deposit [Member]	Dec. 31, 2012 Short-term Deposit [Member]	Mar. 31, 2013 Marketable securities [Member]	Dec. 31, 2012 Marketable securities [Member]	Mar. 31, 2013 Fair Value, Inputs, Level 1 [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 1 [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 1 [Member] Silver ounces received from Mandalay [Member]	Mar. 31, 2013 Fair Value, Inputs, Level 1 [Member] Royalty obligation embedded derivative [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 1 [Member] Royalty obligation embedded derivative [Member]	Mar. 31, 2013 Fair Value, Inputs, Level 1 [Member] Put and call options [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 1 [Member] Put and call options [Member]	Mar. 31, 2013 Fair Value, Inputs, Level 1 [Member] Other derivative instrument [Member]	Mar. 31, 2013 Fair Value, Inputs, Level 1 [Member] Short-term Deposit [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 1 [Member] Short-term Deposit [Member]	Mar. 31, 2013 Fair Value, Inputs, Level 1 [Member] Marketable securities [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 1 [Member] Marketable securities [Member]	Mar. 31, 2013 Fair Value, Inputs, Level 2 [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 2 [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 2 [Member] Silver ounces received from Mandalay [Member]	Mar. 31, 2013 Fair Value, Inputs, Level 2 [Member] Royalty obligation embedded derivative [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 2 [Member] Royalty obligation embedded derivative [Member]	Mar. 31, 2013 Fair Value, Inputs, Level 2 [Member] Put and call options [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 2 [Member] Put and call options [Member]	Mar. 31, 2013 Fair Value, Inputs, Level 2 [Member] Other derivative instrument [Member]	Mar. 31, 2013 Fair Value, Inputs, Level 2 [Member] Short-term Deposit [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 2 [Member] Short-term Deposit [Member]	Mar. 31, 2013 Fair Value, Inputs, Level 2 [Member] Marketable securities [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 2 [Member] Marketable securities [Member]	Mar. 31, 2013 Fair Value, Inputs, Level 3 [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member] Silver ounces received from Mandalay [Member]	Mar. 31, 2013 Fair Value, Inputs, Level 3 [Member] Royalty obligation embedded derivative [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member] Royalty obligation embedded derivative [Member]	Mar. 31, 2013 Fair Value, Inputs, Level 3 [Member] Put and call options [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member] Put and call options [Member]	Mar. 31, 2013 Fair Value, Inputs, Level 3 [Member] Other derivative instrument [Member]	Mar. 31, 2013 Fair Value, Inputs, Level 3 [Member] Short-term Deposit [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member] Short-term Deposit [Member]	Mar. 31, 2013 Fair Value, Inputs, Level 3 [Member] Marketable securities [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member] Marketable securities [Member]	Mar. 31, 2013 Convertible Senior Notes Due March 2028 [Member]	Dec. 31, 2012 Convertible Senior Notes Due March 2028 [Member]	Jan. 29, 2013 7.875% Senior Notes due 2021 [Member]
Assets:
Short-term Deposits									$ 1,498	$ 999											$ 1,498	$ 999											$ 0	$ 0											$ 0	$ 0
Restricted certificates of deposits											23,498	27,065											23,498	27,065											0	0											0	0
Derivative Asset, Fair Value			943												0												943												0
Total assets	24,996	29,007											24,996	28,064											0	943											0	0
Liabilities:
Derivative fair value of derivative liability				121,564	145,098	4,532	9,299	1,225								0	0	0	0	0								121,564	145,098	4,532	9,299	1,225								0	0	0	0	0
Total liabilities	$ 127,321	$ 154,397											$ 0	$ 0											$ 127,321	$ 154,397											$ 0	$ 0
Debt Instrument, Interest Rate, Stated Percentage																																																	3.25%	3.25%	7.875%