Rates and Other Regulatory Activities - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2020 USD ($) customer Dekatherm mi
Electric Limited Proceedings [Member]
Rates and Other Regulatory Activities [Line Items]
Asset Recovery Damaged Property Costs, Noncurrent	$ 1,500,000
Deferred Storm and Property Reserve Deficiency, Noncurrent	$ 800,000
Number of Years to Recover Storm Related Costs	2 years
Hurricane Dorrian [Member]
Rates and Other Regulatory Activities [Line Items]
Extent of Customers Losing Service	100.00%
Asset Recovery Damaged Property Costs, Noncurrent	$ 1,200,000
Amounts Spent to Restore Service	$ 65,000,000.0
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	$ 291,000
Delaware natural gas division [Member]
Rates and Other Regulatory Activities [Line Items]
One time bill credit related to TCJA	1,500,000
Regulatory Liabilities	12,818,000
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	19,209,000
Central Florida Gas Division [Member]
Rates and Other Regulatory Activities [Line Items]
Regulatory Liabilities	8,274,000
Maryland Division [Member]
Rates and Other Regulatory Activities [Line Items]
One time bill credit related to TCJA	400,000
Regulatory Liabilities	4,058,000
Sandpiper [Member]
Rates and Other Regulatory Activities [Line Items]
One time bill credit related to TCJA	600,000
Regulatory Liabilities	3,752,000
FPU electric division [Member]
Rates and Other Regulatory Activities [Line Items]
Regulatory Liabilities	$ 5,704,000
Regulated Energy [Member] | Elkton Gas [Member]
Rates and Other Regulatory Activities [Line Items]
Number of customers acquired through acquisition	7,000