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Oil And Gas Properties (Details) (USD $)
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Oil And Gas Properties [Abstract]      
Oil and gas properties, at cost $ 49,562,000us-gaap_OilAndGasPropertyFullCostMethodGross   $ 49,388,000us-gaap_OilAndGasPropertyFullCostMethodGross
Unevaluated properties 507,000tgc_OilAndGasPropertyUnevaluatedProperties   462,000tgc_OilAndGasPropertyUnevaluatedProperties
Accumulated depletion (25,134,000)us-gaap_OilAndGasPropertyFullCostMethodDepletion   (24,437,000)us-gaap_OilAndGasPropertyFullCostMethodDepletion
Oil and gas properties, net 24,935,000us-gaap_OilAndGasPropertyFullCostMethodNet   25,413,000us-gaap_OilAndGasPropertyFullCostMethodNet
Depletion expense $ 696,000us-gaap_DepletionOfOilAndGasProperties $ 636,000us-gaap_DepletionOfOilAndGasProperties