Business Combinations and Divestitures - Additional Information (Detail) $ in Thousands	9 Months Ended
	Jun. 30, 2024 USD ($) PartnershipUnit	Jun. 30, 2023 USD ($) PartnershipUnit	Sep. 30, 2023 USD ($)
Business Acquisition [Line Items]
Goodwill	$ 268,360		$ 262,103
Heating Oil Businesses
Business Acquisition [Line Items]
Number of businesses acquired | PartnershipUnit	3	2
Cash and assuming	$ 22,600	$ 1,200
Aggregate purchase price allocation, intangible assets	14,400	1,700
Goodwill	6,300	200
Aggregate purchase price allocation, fixed assets	2,800	200
Gross purchase price increased (reduced) by working capital credits	$ (900)	(900)
Cash proceeds from sale of assets		$ 2,200
Propane Dealers
Business Acquisition [Line Items]
Number of businesses acquired | PartnershipUnit	1