Mining Properties (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Mineral Properties, Net [Abstract]
Mining Properties at Cost	$ 600,096	$ 547,998
Accumulated Amortization	(347,920)	(277,841)
Mining Properties at Net Book Value	252,176	270,157
Bogoso/Prestea
Mineral Properties, Net [Abstract]
Mining Properties at Cost	128,713	119,700
Accumulated Amortization	(64,972)	(60,186)
Mining Properties at Net Book Value	63,741	59,514
Bogoso refractory properties
Mineral Properties, Net [Abstract]
Mining Properties at Cost	70,865	70,090
Accumulated Amortization	(40,662)	(34,839)
Mining Properties at Net Book Value	30,203	35,251
Mampon
Mineral Properties, Net [Abstract]
Mining Properties at Cost	16,095	16,095
Accumulated Amortization	0	0
Mining Properties at Net Book Value	16,095	16,095
Wassa/HBB
Mineral Properties, Net [Abstract]
Mining Properties at Cost	352,241	314,801
Accumulated Amortization	(234,847)	(180,486)
Mining Properties at Net Book Value	117,394	134,315
Other
Mineral Properties, Net [Abstract]
Mining Properties at Cost	32,182	27,312
Accumulated Amortization	(7,439)	(2,330)
Mining Properties at Net Book Value	$ 24,743	$ 24,982