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Environmental Matters - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2025 USD ($)
Environmental Restoration Costs
Site Contingency [Line Items]
Estimated Costs Accrued For Remediation	$ 6,500,000
Fitchburg Manufactured Gas Plant Site [Member]
Site Contingency [Line Items]
Remediation costs	3,500,000
Fitchburg Manufactured Gas Plant Site [Member] | Environmental Restoration Costs
Site Contingency [Line Items]
Estimated Costs Accrued For Remediation	$ 40,000

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Amount, before recovery, of expense for known and estimated future costs arising from requirement to perform environmental remediation.

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