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MINERAL PROPERTY INTERESTS AND ASSET RETIREMENT OBLIGATIONS (Details) (USD $)
 12 Months Ended 12 Months Ended 1 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2012
MSC
Jan. 24, 2012
MSC
Dec. 31, 2012
Property holdings in Neveda, acquired in 2007
item
Nov. 30, 2012
One property holding in Neveda, acquired in 2007
Option agreement
Dec. 31, 2012
One property holding in Neveda, acquired in 2007
Option agreement
Dec. 31, 2007
One property holding in Neveda, acquired in 2007
Option agreement
Dec. 31, 2012
Three property holdings in Neveda, acquired in 2007
Dec. 31, 2007
Three property holdings in Neveda, acquired in 2007
Dec. 31, 2012
Mexico property interests
Dec. 31, 2012
Los Azules Copper Project
Dec. 31, 2012
Telken Tenements in Santa Cruz, Argentina
Dec. 31, 2012
Este Tenements in Santa Cruz, Argentina
Dec. 31, 2012
Piramides Tenements in Santa Cruz, Argentina
Dec. 31, 2012
Tobias Tenements in Santa Cruz, Argentina
Dec. 31, 2012
Cerro Mojon Tenements in Santa Cruz, Argentina
Dec. 31, 2012
La Merced Tenements in Santa Cruz, Argentina
Dec. 31, 2012
Cabeza de Vaca Tenements in Santa Cruz, Argentina
Dec. 31, 2012
El Trumai Tenements in Santa Cruz, Argentina
Dec. 31, 2012
Martes 13 Tenements in Santa Cruz, Argentina
Dec. 31, 2012
Celestina Tenements in Santa Cruz, Argentina
Dec. 31, 2012
Tonkin Complex
Dec. 31, 2012
Tonkin Complex
Asset retirement obligation
Dec. 31, 2011
Tonkin Complex
Asset retirement obligation
Dec. 31, 2010
Tonkin Complex
Asset retirement obligation
Dec. 31, 2012
Gold Bar Complex
Dec. 31, 2012
Limo Complex
Dec. 31, 2012
North Battle Mountain Complex in Nevada, United States
Dec. 31, 2012
East Battle Mountain Complex in Nevada, United States
Dec. 31, 2012
West Battle Mountain Complex in Nevada, United States
Dec. 31, 2012
Other United States Properties
Dec. 31, 2012
El Gallo in Mexico
Asset retirement obligation
Dec. 31, 2011
El Gallo in Mexico
Asset retirement obligation
Dec. 31, 2010
El Gallo in Mexico
Asset retirement obligation
Dec. 31, 2012
Other Mexico Exploration Properties in Sinaloa, Mexico
Dec. 31, 2012
Other Argentina exploration properties in San Juan, Argentina
Dec. 31, 2012
Other Argentina exploration properties in Santa Cruz, Argentina
Dec. 31, 2012
El Gallo Complex
Dec. 31, 2012
El Gallo Complex
Gold
oz
Dec. 31, 2012
El Gallo Complex
Silver
oz
Dec. 31, 2012
Tonkin property and Magistral mine portion of the El Gallo Complex
item
Dec. 31, 2012
Minera Andes
Jan. 24, 2012
Minera Andes
Jan. 24, 2012
Minera Andes
MSC
MINERAL PROPERTY INTERESTS                                                                                            
Quantity produced (in ounces)                                                                                 6,863 4,492        
Option to earn interest in property after incurring specified cumulative project related expenditures (as a percent)             51.00%                                                                              
Cumulative project related expenditures to be incurred to earn interest in property             $ 2,400,000                                                                              
Implied value of the option agreement               4,200,000                                                                            
Fair value               4,200,000                                                                            
Interest acquired (as a percent)         49.00%                                                                                 49.00%
Interest held (as a percent)       49.00% 49.00%                                                                                  
Impaired mineral properties           3                                                                                
Impairment charges 18,468,000   5,878,000     18,300,000   14,000,000   2,900,000   1,300,000                                                                    
Deferred income tax           5,900,000                                                                                
Mineral property interests                                                                                         539,092,000  
Carrying value of mineral property interest 767,067,000 245,454,000                     431,190,000 40,234,000 8,121,000 14,815,000 17,719,000 1,971,000 1,891,000 877,000 1,534,000 3,568,000 1,753,000 51,989,000       77,012,000 50,098,000 4,148,000 4,060,000 8,854,000 19,107,000       4,581,000 7,818,000 7,601,000 8,126,000            
Mineral property interest, carrying value before impairment             4,200,000   18,200,000   2,900,000                                                                      
Increase in mineral property interests since acquisition 521,600,000                                                                                     539,100,000    
Exploration and related expenditure costs 47,179,000 42,983,000 19,210,000                                                                                      
Number of most significant properties subject to reclamation obligations                                                                                     2      
Undiscounted estimated reclamation costs                                               3,800,000                               4,600,000            
Cash bonding for mineral properties in the United States 5,183,000 5,190,000                                                                                        
Reclamation expenditures covering all United States properties 100,000 100,000                                                                                        
Credit adjusted risk free rate (as a percent)                                                 8.70% 8.70% 8.70%             6.40% 6.40% 8.70%                    
Inflation rate (as a percent)                                                 3.00% 3.00% 2.00%             3.80% 3.80% 3.30%                    
Changes in the asset retirement obligations                                                                                            
Asset retirement obligation liability - opening balance 6,253,000 6,153,000                                                                                        
Settlements (47,000) (82,000)                                                                                        
Accretion of liability 447,000 524,000 515,000                                                                                      
Adjustment reflecting updated estimates (294,000) (342,000)                                                                                        
Asset retirement obligation liability - ending balance 6,359,000 6,253,000 6,153,000                                                                                      
Current portion of the asset retirement obligation $ 130,000 $ 512,000