Rates and Other Regulatory Activities - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($) Dekatherm customer mi	Dec. 31, 2020 USD ($)
Rates and Other Regulatory Activities [Line Items]
Regulatory Asset - Storm Cost Recovery	$ 45,800
Surcharge - Storm Cost Recovery	7,700
Incremental Revenue - Storm Cost Recovery	$ 3,300
Electric Limited Proceedings [Member]
Rates and Other Regulatory Activities [Line Items]
Extent of Customers Losing Service	100.00%
Hurricane Dorrian [Member]
Rates and Other Regulatory Activities [Line Items]
Regulatory Liability, Amortization Period	30 years
Regulatory Liability, Amortization Period, Revised	10 years
Asset Recovery Damaged Property Costs, Noncurrent	$ 1,200
Delaware natural gas division [Member]
Rates and Other Regulatory Activities [Line Items]
Regulatory Liabilities	12,694	$ 12,728
Maryland Division [Member]
Rates and Other Regulatory Activities [Line Items]
Regulatory Liabilities	3,938	3,970
Sandpiper [Member]
Rates and Other Regulatory Activities [Line Items]
Regulatory Liabilities	3,699	3,713
Central Florida Gas Division [Member]
Rates and Other Regulatory Activities [Line Items]
Regulatory Liabilities	8,146	8,184
Florida Public Utilities Company [Member]
Rates and Other Regulatory Activities [Line Items]
Regulatory Liabilities	19,166	19,257
Fort Meade and Indiantown Divisions [Member]
Rates and Other Regulatory Activities [Line Items]
Regulatory Liabilities	306	309
FPU electric division [Member]
Rates and Other Regulatory Activities [Line Items]
Regulatory Liabilities	6,631	6,694
Eastern Shore Gas Company [Member]
Rates and Other Regulatory Activities [Line Items]
Regulatory Liabilities	34,190	34,190
Elkton Gas [Member]
Rates and Other Regulatory Activities [Line Items]
Regulatory Liabilities	$ 1,124	$ 1,124
Del-Mar Pathway Project [Member] | Eastern Shore Gas Company [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