Rates and Other Regulatory Activities - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2019 USD ($) kWh customer Dekatherm mi
Rates and Other Regulatory Activities [Line Items]
Depreciation Expense Decrease from Depreciation Study Rate Change	$ 900,000
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	$ 800,000
Public Utilities Approved Rate Increase (Decrease), Units | kWh	1,000
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	$ 65,000,000.0
Number of Term Notes to Finance Hurricane Michael	2
Callahan Pipeline [Domain] | Peninsula Pipeline Company [Member]
Rates and Other Regulatory Activities [Line Items]
Number of Pipeline Miles | mi	26
Del-Mar Pathway Project [Member] | Eastern Shore [Member]
Rates and Other Regulatory Activities [Line Items]
Number of Mainline Pipeline Miles | mi	13
Additional Firm Natural Gas Transportation Deliverability | Dekatherm	14,300
number of customers | customer	4
Number of Pipeline Miles | mi	6
Fort Meade and Indiantown Divisions [Member]
Rates and Other Regulatory Activities [Line Items]
Regulatory Liabilities	$ 295,000
Delaware natural gas division [Member]
Rates and Other Regulatory Activities [Line Items]
One time bill credit related to TCJA	1,500,000
Regulatory Liabilities	12,877,000
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	19,168,000
Central Florida Gas Division [Member]
Rates and Other Regulatory Activities [Line Items]
Regulatory Liabilities	8,289,000
Maryland Division [Member]
Rates and Other Regulatory Activities [Line Items]
One time bill credit related to TCJA	400,000
Regulatory Liabilities	4,115,000
Sandpiper [Member]
Rates and Other Regulatory Activities [Line Items]
One time bill credit related to TCJA	600,000
Regulatory Liabilities	3,778,000
FPU electric division [Member]
Rates and Other Regulatory Activities [Line Items]
Regulatory Liabilities	$ 5,789,000