Rates and Other Regulatory Activities - Additional Information (Detail) (USD $)	0 Months Ended	9 Months Ended
	Jun. 13, 2013	Sep. 30, 2014 in mi
Rates and Other Regulatory Activities [Line Items]
PeriodWithinWhichToPerformDepreciationStudy		5 years
MARYLAND
Rates and Other Regulatory Activities [Line Items]
Reduction in accumulated depreciation		$ 3,000,000
Florida [Member]
Rates and Other Regulatory Activities [Line Items]
Public Utilities Interim Rate Increase Decrease Request Amount		2,400,000
Public Utilities, Interim Rate Increase (Decrease), Amount		2,200,000
Public Utilities, Approved Rate Increase (Decrease), Amount		3,800,000
Public Utilities, Approved Return on Equity, Percentage		10.25%
TotalNumberOfElectricitUnitsProposedToBePurchasedUnderContract		20
TermOfThePowerPurchaseAgreement		20 years
Public Utilities, Requested Rate Increase (Decrease), Amount		5,900,000
Estimated Environmental Cleanup Costs To Be Recovered		381,000
Eastern Shore [Member]
Rates and Other Regulatory Activities [Line Items]
NumberOfDaysDuringPeakPeriodSubjectToRightNotToScheduleService		90 days
Proposed Fuel Retention Percentage Rate		0.62%
Deferred Gas Required For Operations Underrecovery Regulatory Balance		494,000
Deferred Cash Out Costs Overrecovery Regulatory Balance		160,000
TETLP Expansion Project [Member] | Eastern Shore [Member]
Rates and Other Regulatory Activities [Line Items]
Increase in Pipeline Capacity		57,000
New plant capacity volume		107,000
White Oak Lateral Project Filing [Member] | Eastern Shore [Member]
Rates and Other Regulatory Activities [Line Items]
Estimated capital cost		$ 11,500,000
White Oak lateral capacity of firm transportation service	55,200
White Oak lateral length of pipeline to be installed		5.5
Lateral diamater of pipeline to be installed		16
New plant capacity volume		55,200