Debt and Capital Lease Obligations (Details Textual) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2012 oz	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Debt and capital lease obligations (Textual) [Abstract]
Current	$ 82,708,000		$ 82,708,000		$ 32,602,000
Accretion of Debt Discount	629,000	576,000	1,241,000	1,137,000
Accretion expense	5,492,000	5,770,000	10,072,000	11,037,000
Borrowing under term facility	50.0		50.0
Maximum Tangible Net Worth of Borrower.	325,000,000
Maximum Tangible Net Worth of Guarantor	1,000,000,000
Outstanding amount of capital leases	17,900,000		17,900,000		27,000,000
Additional Long term debt and capital lease obligations(Textual) [Abstract]
Accretion expense on royalty obligation discount	5,600,000	5,800,000	10,663,000	11,037,000
Remaining Minimum Obligation Under Royalty Agreements	67,100,000		67,100,000		72,100,000
Expensed Interest	7,557,000	9,268,000	14,227,000	18,573,000
Capitalized interest	610,000	238,000	1,694,000	415,000
3.25% Convertible Senior Notes due March 2028 [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	46,786,000		46,786,000		0
Long-term Debt, Fair Value	46,800,000		46,800,000		49,200,000
Carrying value of the equity component					10,900,000
Interest expense	400,000	395,000
Interest Expense, Debt	395,000		791,000	791,000
Debt discount remaining	1,900,000		1,900,000
Effective interest rate on the notes	8.90%		8.90%
Kensington Term Facility [Member]
Debt and capital lease obligations (Textual) [Abstract]
Current	24,248,000		24,248,000		15,398,000
Interest Expense, Debt	906,000	1,162,000	1,880,000	2,267,000
Borrowing under term facility	72,000,000		72,000,000
Protection of gold under gold hedging program	243,750
Weighted average call feature of each collar	1,971.94				1,919.83
Weighted average put feature of each collar	$ 958.16		$ 923.34		$ 951.93
Kensington Term Facility [Member] | Call Option [Member]
Debt and capital lease obligations (Textual) [Abstract]
Gold under collars protection	111,000		111,000		136,000
Kensington Term Facility [Member] | Put Option [Member]
Debt and capital lease obligations (Textual) [Abstract]
Gold under collars protection	156,000		156,000		190,000
Maximum [Member]
Debt and capital lease obligations (Textual) [Abstract]
Debt Equity Ratio	0.4
Minimum [Member]
Debt and capital lease obligations (Textual) [Abstract]
Project Cash Flow to Debt Service Ratio	1.25