Acquisitions - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended	0 Months Ended	3 Months Ended		0 Months Ended		3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	May 31, 2013 Eastern Shore Gas Company [Member] Customer	Mar. 31, 2014 Eastern Shore Gas Company [Member]	Sep. 30, 2013 Eastern Shore Gas Company [Member]	Dec. 02, 2013 Fort Meade [Member]	Feb. 05, 2013 Propane Acquisition [Member] customer	Mar. 31, 2014 Propane Acquisition [Member]
Business Acquisition [Line Items]
Inventory Purchase Accounting Adjustment									$ 271,031
Purchase Price Adjustment						543,000
Number of residential and commercial customers receiving propane gas distribution service				11,000				3,000
Minimum number of customers to whom gas distribution systems and bulk delivery service provided				500
Purchase price allocated to property, plant and equipment				12,600,000			670,000	1,600,000
Purchase price allocated to propane and other inventory				344,000			14,000	231,000
Receivables				2,500,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net				227,000
Revenues	186,337,000	140,729,000			10,300,000
Net Income (Loss) Attributable to Parent	17,681,000	14,869,000	32,787,000		1,700,000
Purchase price allocated to intangible assets related to customer list								300,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life								12 years
Payments to Acquire Businesses, Gross	0	2,437,000		16,500,000			792,000	2,900,000
Sales Tax						726,000
Goodwill	4,625,000		4,354,000				150,000	724,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other							42,000
Goodwill, Purchase Accounting Adjustments									$ 271,000