Business Combinations and Divestitures - Additional Information (Detail) $ in Thousands	3 Months Ended
	Dec. 31, 2023 USD ($) PartnershipUnit	Dec. 31, 2022 USD ($) PartnershipUnit	Sep. 30, 2023 USD ($)
Business Acquisition [Line Items]
Goodwill	$ 262,347		$ 262,103
Heating Oil Businesses
Business Acquisition [Line Items]
Number of businesses acquired | PartnershipUnit	2	2
Cash and assuming	$ 2,500	$ 1,200
Aggregate purchase price allocation, intangible assets	2,700	1,700
Goodwill	200	200
Aggregate purchase price allocation, fixed assets	800	200
Gross purchase price increased (reduced) by working capital credits	$ 1,200	(900)
Cash proceeds from sale of assets		$ 2,200