Rates and Other Regulatory Activities - Additional Information (Detail) (USD $)	0 Months Ended				6 Months Ended	12 Months Ended					12 Months Ended		0 Months Ended		6 Months Ended
	Jun. 13, 2013 in MW mi	Oct. 12, 2012	Oct. 09, 2012	Jan. 02, 2012	Jun. 30, 2013	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012	May 25, 2012 customer	May 14, 2012 Eastern Shore Mainline Expansion Project	Dec. 31, 2013 Florida	Sep. 28, 2012 Florida	May 14, 2013 Eastern Shore Gas Company	Oct. 12, 2012 Eastern Shore Gas Company	Jun. 30, 2013 Natural Gas Operations	Jun. 30, 2013 Electric Operations [Member]
Investment In Affiliates [Line Items]
Legal Fees						$ 1,900,000
Franchise Dispute Litigation Expenses That Recovery Is Allowed						(1,800,000)
Refund Amount To Be Applied To Recover Litigation Expenses						1,800,000
Amortization Period For The Litigation Expense						5 years
Amortization period of regulatory asset											five
Regulatory Assets						69,020,000		80,144,000			1,900,000
Litigation Expenses Recognized In Prior Periods Deferred As Regulatory Asset						1,500,000
Litigation Expenses Recognized In Current Period Deferred As Regulatory Asset						376,000
Regulatory asset which represents portion of the goodwill allowed to be recovered in future rates after the effective date of the Florida PSC order												746,000
Number of dekatherms per day													15,040
Estimated capital cost of Mainline Expansion Project										16,300,000
Number of Customers Filing Motion									2
Extension requested by protesting non-profit organization for public review and comment			60 days
Additional firm transportation service capacity	55,200	17,500
Number of Compressors		3
Estimated capital costs of project	11,200,000													12,100,000
Cycle Power Of Proposed Power Plant	309
Filing period for fuel retention percentage and cash out surcharge							12 months
Curtailment gain				892,000
Curtailment gain, regulatory liability				722,000											464,000	258,000
Amortization Period For The Curtailment Gain Regulatory Liability					34 months
Amortization of Regulatory Liability						510,000
Proposed Fuel Retention Percentage Rate							0.24%
Cash-Our Surcharge							0.00%
Deferred Gas Required For Operations Underrecovery Regulatory Balance							285,000
Deferred Cash Out Costs Overrecovery Regulatory Balance							$ 146,000
Lateral Length Of Pipeline To Be Installed	5.5
Lateral Diameter Of Pipeline To Be Installed	16