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Stock Options (Narrative) (Details) (USD $)
0 Months Ended 12 Months Ended 0 Months Ended
Feb. 01, 2008
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Jan. 05, 2015
Oct. 25, 2000
Stock Options [Line Items]            
Number of shares that may be granted           7,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
Number of additional shares that may be granted 3,500,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized          
Purchase price floor of fair market value   85.00%tgc_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePriceFloorOfFairMarketValue        
Weighted average fair value of options granted   $ 0.22us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue $ 0.25us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue      
Compensation expense   $ 32,000us-gaap_ShareBasedCompensation $ 50,000us-gaap_ShareBasedCompensation $ 52,000us-gaap_ShareBasedCompensation    
Expected volatility   53.30%us-gaap_FairValueAssumptionsExpectedVolatilityRate 47.60%us-gaap_FairValueAssumptionsExpectedVolatilityRate 65.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate    
Risk free interest rate   3.27%us-gaap_FairValueAssumptionsRiskFreeInterestRate 2.97%us-gaap_FairValueAssumptionsRiskFreeInterestRate 2.71%us-gaap_FairValueAssumptionsRiskFreeInterestRate    
Stock Options [Member]            
Stock Options [Line Items]            
Compensation expense   32,000us-gaap_ShareBasedCompensation
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
(28,000)us-gaap_ShareBasedCompensation
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
52,000us-gaap_ShareBasedCompensation
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
   
Current year compensation expense     32,000tgc_ShareBasedCompensationGross
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
     
Reversal of compensation expense     $ 59,500tgc_ReversalOfShareBasedCompensation
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
     
Minimum [Member]            
Stock Options [Line Items]            
Voting power   10.00%tgc_PercentOfVotingPower
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
       
option life remaining   1 month 6 days 1 month 6 days 1 month 6 days    
Maximum [Member]            
Stock Options [Line Items]            
option life remaining   4 years 9 months 18 days 4 years 9 months 18 days 4 years 9 months 18 days    
Voluntary Resignation [Member]            
Stock Options [Line Items]            
Stock Incentive Plan exercisable period   3 months        
10% Of Total Voting Power [Member]            
Stock Options [Line Items]            
Stock Incentive Plan exercisable period   5 years        
Purchase price floor of fair market value   110.00%tgc_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePriceFloorOfFairMarketValue
/ tgc_ShareBasedCompensationVestingPeriodDescriptionAxis
= tgc_TenPercentOfTotalVotingPowerMember
       
Subsequent Event [Member]            
Stock Options [Line Items]            
Options issued to purchase         25,000us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
 
Price per share         $ 0.25us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember