Summary of Significant Accounting Policies - Summary of Property, Plant and Equipment by Classification (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2019 USD ($) mi	Dec. 31, 2018 USD ($) mi
Property, Plant and Equipment [Line Items]
Contributions in Aid of Construction	$ 2,100	$ 2,800
Public Utilities, Allowance for Funds Used During Construction, Description	$ 700	1,900
Number of Months to Establish ROU Asset and Liability	12 months
Property, plant and equipment
Total property, plant and equipment	$ 1,746,532	1,568,441
Less: Accumulated depreciation and amortization	(336,876)	(294,089)
Plus: Construction work in progress	54,141	79,168
Net property, plant and equipment	1,463,797	1,353,520
Natural Gas Distribution [Member] \| Delmarva and Florida [Member]
Property, plant and equipment
Total property, plant and equipment	705,095	657,630
Natural Gas Transmission [Member] \| Delmarva Peninsula, Pennsylvania and Florida [Member]
Property, plant and equipment
Total property, plant and equipment	608,727	537,654
Natural Gas Transmission [Member] \| OHIO
Property, plant and equipment
Total property, plant and equipment	73,658	70,225
Electric distribution \| Florida
Property, plant and equipment
Total property, plant and equipment	127,651	102,133
Propane Operations [Member] \| Mid-Atlantic and Florida [Member]
Property, plant and equipment
Total property, plant and equipment	141,841	123,632
Electricity and Steam Generation [Member] \| Florida
Property, plant and equipment
Total property, plant and equipment	35,436	35,239
Mobile CNG Utility and Pipeline Solutions [Member] \| Florida
Property, plant and equipment
Total property, plant and equipment	14,014	7,240
Other unregulated energy \| Other [Member]
Property, plant and equipment
Total property, plant and equipment	104	104
Other
Property, plant and equipment
Total property, plant and equipment	40,006	34,584
Natural Gas Operations [Member]
Property, plant and equipment
Less: Accumulated depreciation and amortization	(1,500)	$ (1,400)
Net property, plant and equipment	$ 6,700
Miles Of Natural Gas Pipeline \| mi	26	16

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Total increase in earnings in the period representing the cost of equity (based on assumed rate of return) and/or borrowed funds (based on interest rate) used to finance construction of regulated assets, which is expected to be recovered through rate adjustments.

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