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Manufactured Methane Facilities (Narrative) (Details) (USD $) | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Methane Project [Line Items] |  |  |
Depreciation expense | $ 101,000 us-gaap_Depreciation | $ 170,000 us-gaap_Depreciation | $ 258,000 us-gaap_Depreciation
Asset Impairment Charges | 2,796,000 us-gaap_AssetImpairmentCharges |  |
Methane Project [Member] |  |  |
Methane Project [Line Items] |  |  |
Depreciation expense | 163,000 us-gaap_Depreciation / tgc_ExplorationAndProductionRevenueByTypeAxis = tgc_MethaneProjectMember | 136,000 us-gaap_Depreciation / tgc_ExplorationAndProductionRevenueByTypeAxis = tgc_MethaneProjectMember | 101,000 us-gaap_Depreciation / tgc_ExplorationAndProductionRevenueByTypeAxis = tgc_MethaneProjectMember
Asset Impairment Charge Net Of Tax | $ 1,700,000 tgc_AssetImpairmentChargeNetOfTax / tgc_ExplorationAndProductionRevenueByTypeAxis = tgc_MethaneProjectMember |  |

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- Definition Asset Impairment Charge Net Of Tax + References No definition available. + Details
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- Details
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- Definition Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=8077374&loc=d3e2420-110228 + Details
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- Definition The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 + Details
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