DERIVATIVE LOSSES (Details) In Thousands, except Share data in Millions, unless otherwise specified	3 Months Ended		9 Months Ended		3 Months Ended			9 Months Ended		3 Months Ended		9 Months Ended				3 Months Ended		9 Months Ended
	Sep. 30, 2012 USD ($)	Sep. 30, 2011 USD ($)	Sep. 30, 2012 USD ($)	Sep. 30, 2011 USD ($)	Sep. 30, 2012 Riverstone Resources, Inc. - warrants USD ($)	Sep. 30, 2011 Riverstone Resources, Inc. - warrants USD ($)	Mar. 31, 2008 Riverstone Resources, Inc. - warrants CAD	Sep. 30, 2012 Riverstone Resources, Inc. - warrants USD ($)	Sep. 30, 2011 Riverstone Resources, Inc. - warrants USD ($)	Sep. 30, 2012 Gold price derivatives USD ($)	Sep. 30, 2011 Gold price derivatives USD ($)	Sep. 30, 2012 Gold price derivatives USD ($)	Sep. 30, 2011 Gold price derivatives USD ($)	Feb. 28, 2011 Gold price derivatives oz	Jan. 31, 2011 Gold price derivatives oz	Sep. 30, 2012 Riverstone Resources, Inc. - warrants and Gold Price derivatives USD ($)	Sep. 30, 2011 Riverstone Resources, Inc. - warrants and Gold Price derivatives USD ($)	Sep. 30, 2012 Riverstone Resources, Inc. - warrants and Gold Price derivatives USD ($)	Sep. 30, 2011 Riverstone Resources, Inc. - warrants and Gold Price derivatives USD ($)
Derivative [Line Items]
Derivative loss	$ 0	$ 11,161	$ 162	$ 17,840	$ 0	$ 25		$ 162	$ 67	$ 0	$ 11,136	$ 0	$ 17,773
Realized (gain) / loss																0	9,461	162	10,960
Unrealized loss	$ 0	$ (1,700)	$ (162)	$ (6,879)												$ 0	$ 1,700	$ 0	$ 6,880
Warrants issued							2.0
Warrants exercise price (CDN$ per share)							0.45
Notional amount of derivative (ounces)														75,200	76,800
Derivative floor price (US$ per ounce)														1,200	1,200
Derivative cap price (US$ per ounce)														1,503	1,457