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Commitments And Contingencies (Narrative) (Details) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
May 31, 2017
May 31, 2016
May 31, 2015
Commitments And Contingencies [Line Items]            
Rent expense $ 73,000us-gaap_OperatingLeasesRentExpenseNet $ 92,000us-gaap_OperatingLeasesRentExpenseNet $ 80,000us-gaap_OperatingLeasesRentExpenseNet      
Maximum range of possible payment 386,000us-gaap_LossContingencyRangeOfPossibleLossMaximum          
Denver Colorado [Member]            
Commitments And Contingencies [Line Items]            
Lease term 38 months          
Number of free months in lease 2 months          
Leases rent due per month 2,700tgc_OperatingLeasesRentExpensePerPeriod
/ us-gaap_StatementGeographicalAxis
= tgc_DenverColoradoMember
         
Lease due in 2015 48,000us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent
/ us-gaap_StatementGeographicalAxis
= tgc_DenverColoradoMember
         
Lease due in 2016 50,000us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears
/ us-gaap_StatementGeographicalAxis
= tgc_DenverColoradoMember
         
Lease due in 2017 21,000us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears
/ us-gaap_StatementGeographicalAxis
= tgc_DenverColoradoMember
         
Scenario, Forecast [Member]            
Commitments And Contingencies [Line Items]            
Leases rent due per month       $ 4,216.81tgc_OperatingLeasesRentExpensePerPeriod
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioForecastMember
$ 4,090.94tgc_OperatingLeasesRentExpensePerPeriod
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioForecastMember
$ 3,965.06tgc_OperatingLeasesRentExpensePerPeriod
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioForecastMember