Debt and Capital Lease Obligations (Details Textual) (USD $)	3 Months Ended		9 Months Ended			3 Months Ended		9 Months Ended				0 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended						9 Months Ended			9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011	Sep. 30, 2012 3.25% Convertible Senior Notes due March 2028 [Member]	Sep. 30, 2011 3.25% Convertible Senior Notes due March 2028 [Member]	Sep. 30, 2012 3.25% Convertible Senior Notes due March 2028 [Member]	Sep. 30, 2011 3.25% Convertible Senior Notes due March 2028 [Member]	Dec. 31, 2011 3.25% Convertible Senior Notes due March 2028 [Member]	Sep. 30, 2012 Debt After Step Down [Member]	Aug. 16, 2012 Kensington Term Facility [Member]	Sep. 30, 2012 Kensington Term Facility [Member] oz	Sep. 30, 2011 Kensington Term Facility [Member]	Sep. 30, 2012 Kensington Term Facility [Member]	Sep. 30, 2011 Kensington Term Facility [Member]	Dec. 31, 2011 Kensington Term Facility [Member]	Sep. 30, 2012 Kensington Term Facility [Member] Call Option [Member] oz	Dec. 31, 2011 Kensington Term Facility [Member] Call Option [Member] oz	Sep. 30, 2012 Kensington Term Facility [Member] Put Option [Member] oz	Dec. 31, 2011 Kensington Term Facility [Member] Put Option [Member] oz	Mar. 31, 2012 Minimum [Member]	Sep. 30, 2012 LIBOR [Member]	Sep. 30, 2012 LIBOR [Member] Maximum [Member]	Sep. 30, 2012 LIBOR [Member] Minimum [Member]	Sep. 30, 2012 Alternate Base Rate [Member]	Sep. 30, 2012 Alternate Base Rate [Member] Maximum [Member]	Sep. 30, 2012 Alternate Base Rate [Member] Minimum [Member]
Debt and capital lease obligations (Textual) [Abstract]
Interest rate on notes						3.25%		3.25%
Principal amount of bank loan						$ 48,700,000		$ 48,700,000
Current	56,340,000		56,340,000		32,602,000	47,424,000		47,424,000		0			0		0		15,398,000
Long-term Debt, Fair Value						49,600,000		49,600,000		49,200,000
Carrying value of the equity component										10,900,000
Interest expense						400,000	395,000
Interest Expense, Debt						395,000		1,186,000	1,186,000				459,000	1,086,000	2,339,000	3,353,000
Accretion of Debt Discount	639,000	585,000	1,879,000	1,722,000
Accretion expense	4,276,000	4,990,000	14,348,000	16,027,000
Debt discount remaining						1,200,000		1,200,000
Effective interest rate on the notes						8.90%		8.90%
Borrowing under term facility	0		0
Line of Credit Facility, Increase, Additional Borrowings			0
Line of Credit Facility, Commitment Fee Amount	0.1
Debt Instrument, Basis Spread on Variable Rate																								3.25%	2.25%		2.25%	1.25%
Ratio of consolidated debt to adjusted EBITDA	3.25		3.25								3
Ratio of adjusted EBITDA to interest expense	3		3
Percentage of tangible net worth																						90.00%
Percentage of net income	25.00%
Repayments of Long-term Debt												68,600,000
Debt Instrument, Description of Variable Rate Basis																							LIBOR			alternate base rate
Protection of gold under gold hedging program													243,750
Gold under collars protection																		104,000	136,000	139,000	190,000
Weighted average call feature of each collar													1,970.05				1,919.83
Weighted average put feature of each collar													962.42		923.34		951.93
Outstanding amount of capital leases	14,000,000		14,000,000		27,000,000
Additional Long term debt and capital lease obligations(Textual) [Abstract]
Accretion expense on royalty obligation discount	4,400,000	5,400,000	15,047,000	16,407,000
Remaining Minimum Obligation Under Royalty Agreements	64,100,000		64,100,000		72,100,000
Expensed Interest	7,351,000	7,980,000	21,578,000	26,553,000
Capitalized interest	$ 512,000	$ 886,000	$ 2,206,000	$ 1,302,000