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MINERAL PROPERTY INTERESTS AND ASSET RETIREMENT OBLIGATIONS (Details) (USD $) | 3 Months Ended | 6 Months Ended | 12 Months Ended |  | 6 Months Ended |
--- | --- | --- | --- | --- | --- | ---
Jun. 30, 2012 | Jun. 30, 2011 | Jun. 30, 2012 | Jun. 30, 2011 | Dec. 31, 2011 | Jun. 30, 2012 Tonkin Complex | Jun. 30, 2012 Gold Bar Complex | Jun. 30, 2012 Limo Complex | Jun. 30, 2012 Battle Mountain Complex | Jun. 30, 2012 Other United States Properties | Jun. 30, 2012 Los Azules Copper Project | Jun. 30, 2012 Other Argentina exploration properties in San Juan, Argentina | Jun. 30, 2012 Cerro Negro Region | Jun. 30, 2012 Other Argentina exploration properties in Santa Cruz, Argentina | Jun. 30, 2012 Other Argentina exploration properties in Catamarca, Argentina | Jun. 30, 2012 Other Argentina exploration properties in Chubut, Argentina | Jun. 30, 2012 El Gallo Complex | Jun. 30, 2012 Other Mexico Exploration Properties in Sinaloa, Mexico | Jun. 30, 2012 Tonkin property and Magistral mine portion of the El Gallo Complex item | Jun. 30, 2012 Minera Andes | Jan. 24, 2012 Minera Andes
MINERAL PROPERTY INTERESTS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mineral property interests |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 597,374,000
Total | 843,764,000 |  | 843,764,000 |  | 245,454,000 | 52,430,000 | 77,012,000 | 50,098,000 | 31,106,000 | 22,009,000 | 486,862,000 | 7,819,000 | 80,889,000 | 19,194,000 | 2,362,000 | 248,000 | 9,469,000 | 4,266,000 |  |  |
Increase in mineral property interests since acquisition |  |  | 598,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 597,400,000 |
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 | 5,190,000 |  | 5,190,000 |  | 5,190,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Changes in the asset retirement obligations |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Asset retirement obligation liability - opening balance |  |  | 6,253,000 | 6,153,000 | 6,153,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlements |  |  | (14,000) |  | (82,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Accretion of liability | 120,000 | 137,000 | 232,000 | 266,000 | 524,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Adjustment reflecting updated estimates |  |  | 147,000 |  | (342,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Asset retirement obligation liability - ending balance | 6,618,000 |  | 6,618,000 |  | 6,253,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Current portion of the asset retirement obligation | $ 510,000 |  | $ 510,000 |  | $ 512,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

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- Definition Current portion of reclamation reserve to restore a mining or drilling site to the condition agreed upon within the mining or drilling contract. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 43 -Section A -Paragraph 8 -Chapter 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 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20 -Article 5 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.20) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6361293&loc=d3e6911-107765 + 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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