Environmental Commitments and Contingencies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2021 USD ($) site	Dec. 31, 2020 USD ($)
Environmental Commitments And Contingencies [Line Items]
Companys Exposure In Number Of Former Manufactured Gas Plant Sites | site	7
Environmental liabilities	$ 3,538,000	$ 4,299,000
Manufactured Gas Plant
Environmental Commitments And Contingencies [Line Items]
Regulatory assets for future recovery of environmental costs	1,300,000	1,700,000
Maximum
Environmental Commitments And Contingencies [Line Items]
Environmental Remediation Expense	900,000
Minimum
Environmental Commitments And Contingencies [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	300,000
West Palm Beach Florida | Maximum
Environmental Commitments And Contingencies [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	14,200,000
West Palm Beach Florida | Minimum
Environmental Commitments And Contingencies [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	3,300,000
FPU
Environmental Commitments And Contingencies [Line Items]
Environmental liabilities	5,200,000	5,900,000
Approval of recovery of environmental costs	14,000,000
Environmental costs recovered	12,900,000	12,400,000
FPU | Manufactured Gas Plant
Environmental Commitments And Contingencies [Line Items]
Regulatory assets for future recovery of environmental costs	$ 1,100,000	$ 1,600,000