Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Dec. 31, 2012 Silver ounces received from Mandalay [Member]	Jun. 30, 2013 Royalty obligation embedded derivative [Member]	Dec. 31, 2012 Royalty obligation embedded derivative [Member]	Dec. 31, 2012 Put and call options [Member]	Jun. 30, 2013 Rochester NSR royalty obligation [Member]	Jun. 30, 2013 Other derivative instrument [Member]	Dec. 31, 2012 Short-term Deposit [Member]	Jun. 30, 2013 Marketable securities [Member]	Dec. 31, 2012 Marketable securities [Member]	Jun. 30, 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]	Jun. 30, 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]	Dec. 31, 2012 Fair Value, Inputs, Level 1 [Member] Put and call options [Member]	Jun. 30, 2013 Fair Value, Inputs, Level 1 [Member] Rochester NSR royalty obligation [Member]	Jun. 30, 2013 Fair Value, Inputs, Level 1 [Member] Other derivative instrument [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 1 [Member] Short-term Deposit [Member]	Jun. 30, 2013 Fair Value, Inputs, Level 1 [Member] Marketable securities [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 1 [Member] Marketable securities [Member]	Jun. 30, 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]	Jun. 30, 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]	Dec. 31, 2012 Fair Value, Inputs, Level 2 [Member] Put and call options [Member]	Jun. 30, 2013 Fair Value, Inputs, Level 2 [Member] Rochester NSR royalty obligation [Member]	Jun. 30, 2013 Fair Value, Inputs, Level 2 [Member] Other derivative instrument [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 2 [Member] Short-term Deposit [Member]	Jun. 30, 2013 Fair Value, Inputs, Level 2 [Member] Marketable securities [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 2 [Member] Marketable securities [Member]	Jun. 30, 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]	Jun. 30, 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]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member] Put and call options [Member]	Jun. 30, 2013 Fair Value, Inputs, Level 3 [Member] Rochester NSR royalty obligation [Member]	Jun. 30, 2013 Fair Value, Inputs, Level 3 [Member] Other derivative instrument [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member] Short-term Deposit [Member]	Jun. 30, 2013 Fair Value, Inputs, Level 3 [Member] Marketable securities [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member] Marketable securities [Member]	Jun. 30, 2013 Convertible Senior Notes Due March 2028 [Member]	Dec. 31, 2012 Convertible Senior Notes Due March 2028 [Member]	Jun. 30, 2013 7.875% Senior Notes due 2021 [Member]	Jan. 29, 2013 7.875% Senior Notes due 2021 [Member]
Assets:
Short-term Deposits									$ 999											$ 999											$ 0											$ 0
Restricted certificates of deposits										16,008	27,065										16,008	27,065										0	0										0	0
Derivative Asset, Fair Value	2,358		943									0		0									2,358		943									0		0
Total assets	18,366	29,007										16,008	28,064										2,358	943										0	0
Liabilities:
Derivative fair value of derivative liability				52,359	145,098	9,299	22,046	2,554							0	0	0	0	0							52,359	145,098	9,299	22,046	2,554							0	0	0	0	0
Total liabilities	$ 76,959	$ 154,397										$ 0	$ 0										$ 76,959	$ 154,397										$ 0	$ 0
Debt Instrument, Interest Rate, Stated Percentage																																													3.25%	3.25%	7.875%	7.875%