Rates and Other Regulatory Activities - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2020 USD ($) customer Dekatherm mi
Rates and Other Regulatory Activities [Line Items]
Regulatory Asset - Storm Cost Recovery	$ 45,800,000
Surcharge - Storm Cost Recovery	7,700,000
Incremental Revenue - Storm Cost Recovery	$ 3,300,000
Electric Limited Proceedings [Member]
Rates and Other Regulatory Activities [Line Items]
Extent of Customers Losing Service	100.00%
Asset Recovery Damaged Property Costs, Noncurrent	$ 1,500,000
Deferred Storm and Property Reserve Deficiency, Noncurrent	800,000
Amounts Spent to Restore Service	65,000,000.0
Hurricane Dorrian [Member]
Rates and Other Regulatory Activities [Line Items]
Asset Recovery Damaged Property Costs, Noncurrent	$ 1,200,000
Regulatory Liability, Amortization Period	30 years
Regulatory Liability, Amortization Period, Revised	10 years
Eastern Shore [Member]
Rates and Other Regulatory Activities [Line Items]
Cost Recovery, Capital	$ 500,000
Callahan Pipeline [Domain] | Peninsula Pipeline Company [Member]
Rates and Other Regulatory Activities [Line Items]
Number of Pipeline Miles | mi	26
Callahan Project [Member] | Peninsula Pipeline [Member]
Rates and Other Regulatory Activities [Line Items]
Diameter of Pipe | mi	16
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	$ 309,000
Delaware natural gas division [Member]
Rates and Other Regulatory Activities [Line Items]
One time bill credit related to TCJA	1,500,000
Regulatory Liabilities	12,758,000
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	19,192,000
Central Florida Gas Division [Member]
Rates and Other Regulatory Activities [Line Items]
Regulatory Liabilities	8,214,000
Maryland Division [Member]
Rates and Other Regulatory Activities [Line Items]
One time bill credit related to TCJA	365,000
Regulatory Liabilities	4,000,000
Sandpiper [Member]
Rates and Other Regulatory Activities [Line Items]
One time bill credit related to TCJA	608,000
Regulatory Liabilities	3,726,000
FPU electric division [Member]
Rates and Other Regulatory Activities [Line Items]
Regulatory Liabilities	6,758,000
Elkton Gas [Member]
Rates and Other Regulatory Activities [Line Items]
One time bill credit related to TCJA	47,000
Regulatory Liabilities	$ 1,124,000
Regulated Energy [Member] | Elkton Gas [Member]
Rates and Other Regulatory Activities [Line Items]
Number of customers acquired through acquisition	7,000