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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 |
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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 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

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- Definition The amount of acquisition cost of a business combination allocated to mineral rights for acquired entities in the mining industry. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 141 -Paragraph 51 -Subparagraph e -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Emerging Issues Task Force (EITF) -Number 04-3 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Emerging Issues Task Force (EITF) -Number 04-2 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. + Details
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- Definition The charge against earnings in the period for known or estimated future costs arising from requirements to perform environmental remediation activities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 96-1 -Paragraph 170 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 96-1 -Paragraph 147, 148, 149, 150 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 5 -Paragraph 9, 10 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Emerging Issues Task Force (EITF) -Number 90-8 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13296-110859 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 143 -Paragraph 2 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. + Details
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- Definition The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 159 -Paragraph 18 -Subparagraph f -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 20 -Subparagraph a (1) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. + Details
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- Definition Exploration expenses (including prospecting) related to the mining industry would be included in operating expenses. Exploration costs include costs incurred in identifying areas that may warrant examination and in examining specific areas that are considered to have prospects of mineral reserves. + References No definition available. + Details
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- Definition Risk-free interest rate assumption used in valuing an instrument. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258 + Details
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- Definition The noncurrent cash, cash equivalents and investments that is restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits classified as long-term; that is not expected to be released from such existing restrictions within one year of the balance sheet date or operating cycle, whichever is longer. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. Includes noncurrent cash equivalents and investments that are similarly restricted as to withdrawal, usage or disposal. + References No definition available. + Details
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