Long-Term Debt and Capital Lease Obligations (Details Textual) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Debt and capital lease obligations (Textual) [Abstract]
Current	$ 80,857,000		$ 32,602,000
Accretion expense	4,580,000	5,267,000
Maximum Tangible Net Worth of Borrower.	325,000,000
Maximum Tangible Net Worth of Guarantor	1,000,000,000
Outstanding amount of capital leases	22,800,000		27,000,000
Additional Long term debt and capital lease obligations(Textual) [Abstract]
Accretion expense on royalty obligation discount	5,100,000	5,300,000
Remaining Minimum Obligation Under Royalty Agreements	69,100,000		72,100,000
Expensed Interest	6,670,000	9,304,000
Capitalized interest	1,083,000	178,000
3.25% Convertible Senior Notes due March 2028 [Member]
Debt and capital lease obligations (Textual) [Abstract]
Interest rate on notes	3.25%
Principal amount of bank loan	48,700,000
Current	46,157,000		0
Percentage of principal amount of notes to be repurchased, plus accrued and unpaid interest equivalent to repurchase price	100.00%
Initial conversion rate of common stock per $1000 principal amount of notes	17.60254
Per principal amount of notes convertible into specified number of common stock	1,000
Initial conversion price	$ 56.81
Long-term Debt, Fair Value	48,700,000		49,200,000
Carrying value of the equity component	10,900,000		10,900,000
Interest expense	0	400,000
Accretion expense	600,000	600,000
Debt discount remaining	2,500,000
Effective interest rate on the notes	8.90%
Kensington Term Facility [Member]
Debt and capital lease obligations (Textual) [Abstract]
Current	21,747,000		15,398,000
Borrowing under term facility	75,800,000
Protection of gold under gold hedging program	243,750
Weighted average call feature of each collar	1,919.83
Weighted average put feature of each collar	$ 954.74
Kensington Term Facility [Member] | Call Option [Member]
Debt and capital lease obligations (Textual) [Abstract]
Gold under collars protection	136,000
Kensington Term Facility [Member] | Put Option [Member]
Debt and capital lease obligations (Textual) [Abstract]
Gold under collars protection	173,000
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