Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2012 Silver ounces received from Mandalay [Member]	Sep. 30, 2013 Royalty obligation embedded derivative [Member]	Dec. 31, 2012 Royalty obligation embedded derivative [Member]	Dec. 31, 2012 Put and call options [Member]	Sep. 30, 2013 Rochester NSR royalty obligation [Member]	Sep. 30, 2013 Other derivative instrument [Member]	Dec. 31, 2012 Short-term Deposit [Member]	Sep. 30, 2013 Marketable securities [Member]	Dec. 31, 2012 Marketable securities [Member]	Sep. 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]	Sep. 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]	Sep. 30, 2013 Fair Value, Inputs, Level 1 [Member] Rochester NSR royalty obligation [Member]	Sep. 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]	Sep. 30, 2013 Fair Value, Inputs, Level 1 [Member] Marketable securities [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 1 [Member] Marketable securities [Member]	Sep. 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]	Sep. 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]	Sep. 30, 2013 Fair Value, Inputs, Level 2 [Member] Rochester NSR royalty obligation [Member]	Sep. 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]	Sep. 30, 2013 Fair Value, Inputs, Level 2 [Member] Marketable securities [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 2 [Member] Marketable securities [Member]	Sep. 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]	Sep. 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]	Sep. 30, 2013 Fair Value, Inputs, Level 3 [Member] Rochester NSR royalty obligation [Member]	Sep. 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]	Sep. 30, 2013 Fair Value, Inputs, Level 3 [Member] Marketable securities [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member] Marketable securities [Member]	Sep. 30, 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]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Expected Royalty Duration, Rochester	4 years 8 months 5 days
Assets:
Short-term Deposits									$ 999											$ 999											$ 0											$ 0
Restricted certificates of deposits										17,616	27,065											27,065										0	0										0	0
Available-for-sale Securities, Equity Securities, Noncurrent		27,065																			17,616
Derivative Asset, Fair Value	160		943									0		0									160		943									0		0
Total assets	17,776	29,007										17,616	28,064										160	943										0	0
Liabilities:
Derivative fair value of derivative liability				61,996	145,098	9,299	24,409	2,069							0	0	0	0	0							61,996	145,098	9,299	0	2,069							0	0	0	24,409	0
Total liabilities	$ 88,474	$ 154,397										$ 0	$ 0										$ 64,065	$ 154,397										$ 24,409	$ 0
Debt Instrument, Interest Rate, Stated Percentage																																													3.25%	3.25%	7.875%