Rates and Other Regulatory Activities - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2019 USD ($) kWh
Electric Limited Proceedings [Member]
Rates and Other Regulatory Activities [Line Items]
Dollar Amount of Term Notes to Finance Hurricane Michael Costs	$ 30,000,000
Extent of Customers Losing Service	100.00%
Basis Plus LIBOR for Term Notes to Finance Hurricane Michael Costs	75
Public Utilities, Approved Rate Increase (Decrease), Amount	$ 1.54
Asset Recovery Damaged Property Costs, Noncurrent	1,500,000
Deferred Storm and Property Reserve Deficiency, Noncurrent	$ 779,000
Public Utilities Approved Rate Increase (Decrease), Units | kWh	1,000.00
Number of Years to Recover Storm Related Costs	2 years
Number of Months for Term Notes to Finance Hurricane Michael	13 months
Amounts Spent to Restore Service	$ 65,000,000
Number of Term Notes to Finance Hurricane Michael	2
Delaware natural gas division [Member]
Rates and Other Regulatory Activities [Line Items]
Regulatory Liabilities	$ 13,082,000
Eastern Shore [Member]
Rates and Other Regulatory Activities [Line Items]
One time bill credit related to TCJA	900,000
Regulatory Liabilities	34,190,000
Florida Public Utilities Company [Member]
Rates and Other Regulatory Activities [Line Items]
Regulatory Liabilities	19,478,000
Central Florida Gas Division [Member]
Rates and Other Regulatory Activities [Line Items]
Regulatory Liabilities	8,346,000
Maryland Division [Member]
Rates and Other Regulatory Activities [Line Items]
One time bill credit related to TCJA	365,000
Regulatory Liabilities	4,171,000
Sandpiper [Member]
Rates and Other Regulatory Activities [Line Items]
One time bill credit related to TCJA	608,000
Regulatory Liabilities	3,803,000
FPU electric division [Member]
Rates and Other Regulatory Activities [Line Items]
Regulatory Liabilities	$ 5,950,000