Environmental Commitments and Contingencies - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2023 USD ($) site	Dec. 31, 2022 USD ($)
Environmental Commitments And Contingencies [Line Items]
Company's exposure in number of former Manufactured Gas Plant Sites | site	7
Environmental liabilities	$ 2,512,000	$ 3,272,000
Seaford [Member] | Minimum [Member]
Environmental Commitments And Contingencies [Line Items]
Estimated costs of remediation range, minimum	300,000
Seaford [Member] | Maximum [Member]
Environmental Commitments And Contingencies [Line Items]
Estimated costs of remediation range, minimum	900,000
Manufactured Gas Plant [Member]
Environmental Commitments And Contingencies [Line Items]
Regulatory Assets for future recovery of environmental costs	500,000	800,000
FPU [Member]
Environmental Commitments And Contingencies [Line Items]
Environmental liabilities	3,400,000	$ 4,300,000
Approval of recovery of environmental costs	$ 14,000,000