Income Taxes - Federal Statutory Rate to Pre-Tax Income from Continuing Operations (Detail) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Tax expense at statutory rate of 34%	$ 2,015,101	$ 3,372,404	$ 2,065,991
State income tax, net of Federal tax expense	307,099	348,151	228,051
Amortization of deferred investment tax credits	(21,062)	(21,062)	(21,062)
Change in valuation allowance	(397,619)	(237,557)	(262,343)
Permanent differences	24,580	134,583	140,211
State rate change	149,015	(346,149)	0
Other	87,878	(2,825)	206,277
Total income tax expense	2,164,992egas_IncomeTaxExpenseBenefitNet	3,247,545egas_IncomeTaxExpenseBenefitNet	2,357,125egas_IncomeTaxExpenseBenefitNet
Income tax expense from discontinued operations	(617,410)	(223,834)	(400,326)
Income tax expense from continuing operations	$ 1,547,582us-gaap_IncomeTaxExpenseBenefit	$ 3,023,711us-gaap_IncomeTaxExpenseBenefit	$ 1,956,799us-gaap_IncomeTaxExpenseBenefit

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Amount of current income tax expense (benefit) net and deferred income tax expense (benefit) pertaining to continuing operations.

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Income tax reconciliation adjustment for state tax rate change.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to increase (decrease) in the valuation allowance for deferred tax assets.

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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