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MINERAL PROPERTY INTERSTS AND ASSET RETIREMENT OBLIGATIONS (Details) (USD $) | 3 Months Ended | 9 Months Ended | 12 Months Ended | 9 Months Ended |  | 3 Months Ended | 9 Months Ended | 3 Months Ended | 9 Months Ended | 3 Months Ended | 9 Months Ended | 3 Months Ended | 9 Months Ended | 3 Months Ended | 9 Months Ended
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Sep. 30, 2014 | Sep. 30, 2013 | Sep. 30, 2014 | Sep. 30, 2013 | Dec. 31, 2013 | Sep. 30, 2014 Argentina | Sep. 30, 2013 Argentina | Sep. 30, 2014 Tonkin property and El Gallo 1 mine portion of the El Gallo Complex item | Sep. 30, 2014 Tonkin Complex | Sep. 30, 2014 El Gallo mine | Sep. 30, 2014 El Gallo mine | Sep. 30, 2013 Telken Tenements Argentina | Sep. 30, 2013 Este Tenements Argentina | Sep. 30, 2013 Piramides Tenements Argentina | Sep. 30, 2013 Tobias Tenements Argentina | Sep. 30, 2013 West Battle Mountain Complex Nevada | Sep. 30, 2013 West Battle Mountain Complex Nevada | Sep. 30, 2013 Exploration properties in Santa Cruz, Argentina Nevada | Sep. 30, 2013 Exploration properties in Santa Cruz, Argentina Nevada | Sep. 30, 2013 Exploration properties located in Santa Cruz, Nevada | Sep. 30, 2013 Exploration properties located in Santa Cruz, Nevada | Jun. 30, 2014 Los Azules Copper Project | Sep. 30, 2014 Los Azules Copper Project | Sep. 30, 2014 Los Azules Copper Project Argentina
Mineral Property Interests [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of most significant properties subject to reclamation obligations |  |  |  |  |  |  |  | 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Undiscounted estimated reclamation costs |  |  |  |  |  |  |  |  | $ 2,700,000 | $ 4,600,000 | $ 4,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Cash bonding for mineral properties in the United States | 2,000 |  | 2,000 |  | 5,183,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Reduction in cash bonding requirements |  |  | (5,181,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of annual fees on surety bonds |  |  | 1.50% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of upfront deposit on surety bonds |  |  | 10.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amortization of mineral property interests and asset retirement obligations |  |  | 923,000 | 1,244,000 |  |  |  |  |  | 300,000 | 1,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Amortization of capitalized asset retirement costs |  |  |  |  |  |  |  |  |  | 100,000 | 400,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Impairment charges |  | 6,287,000 | 120,398,000 | 34,016,000 |  | 120,398,000 | 27,729,000 |  |  |  |  | 13,792,000 | 2,784,000 | 5,079,000 | 6,074,000 | 6,287,000 | 6,287,000 | 6,300,000 | 6,300,000 | 27,700,000 | 27,700,000 | 120,400,000 |  | 120,398,000
Recovery of deferred income tax | 22,500,000 | 2,200,000 | 22,500,000 | 7,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  | 2,200,000 | 2,200,000 | 2,300,000 | 2,300,000 |  | 22,500,000 |
Changes in the asset retirement obligations |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Asset retirement obligation liability, beginning balance |  |  | 7,247,000 | 6,359,000 | 6,359,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlements |  |  | (43,000) |  | (60,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Accretion of liability | 100,000 | 113,000 | 309,000 | 347,000 | 461,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Adjustment reflecting updated estimates |  |  | (79,000) |  | 487,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Asset retirement obligation liability, ending balance | 7,434,000 |  | 7,434,000 |  | 7,247,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Current portion of the asset retirement obligation | $ 1,458,000 |  | $ 1,458,000 |  | $ 1,392,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

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