Acquisitions - Additional Information (Detail) (USD $)	0 Months Ended	3 Months Ended	6 Months Ended			6 Months Ended
	May 31, 2013 gal sites	Jun. 30, 2013	Jun. 30, 2013	Jun. 07, 2013	Dec. 31, 2012	Jun. 30, 2013 Eastern Shore Gas Company [Member] Customer	Jun. 30, 2013 Propane Acquisition [Member] Customer	Feb. 05, 2013 Propane Acquisition [Member]
Business Acquisition [Line Items]
Purchase price	$ 16,500,000			$ 600,000				$ 2,900,000
Transaction costs, tax	759,000
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	13,200,000			105,000				1,600,000
Purchase price allocated to propane and other inventory	309,000			94,000				502,000
Net assets	2,400,000
Receivables	212,000
Number of leased propane tanks	13
Storage capacity of leased propane tanks	570,000
Duration of lease of propane tanks	6 years
Monthly fee payment in year one	42,000
Monthly fee payment, year two to six	125,000
Annual Estimate Of Volume Of Propane To Be Purchased	7,400,000
Number of years to purchase propane under contract	6 years
Capital Lease Obligations	7,100,000	7,105,000	7,105,000		0
Amortization expense		21,000
Capital lease asset	7,100,000
Amortization of leased asset			21,000
Purchase price allocated to intangible assets related to customer list				250,000				300,000
Purchase price allocated to goodwill				173,000
Sales Tax		759,000	759,000
Goodwill		$ 4,716,000	$ 4,716,000		$ 4,090,000			$ 453,000