Business Combinations - Additional Information (Detail) $ in Thousands	12 Months Ended
	Sep. 30, 2022 USD ($) PartnershipUnit	Sep. 30, 2021 USD ($) PartnershipUnit	Sep. 30, 2020 USD ($) PartnershipUnit
Business Acquisition [Line Items]
Goodwill	$ 254,110	$ 253,398	$ 240,327
Heating Oil Dealers
Business Acquisition [Line Items]
Number of businesses acquired | PartnershipUnit	5	3	2
Aggregate purchase price partnership acquired	$ 15,600	$ 42,500	$ 3,300
Cash and assuming	13,100	40,700	3,000
Liabilities	2,500	1,800	300
Aggregate purchase price allocation, intangible assets	7,300
Goodwill	3,100
Aggregate purchase price allocation, goodwill and intangible assets		37,300	3,200
Aggregate purchase price allocation, fixed assets	5,600	6,200	600
Gross purchase price increased (reduced) by working capital credits	$ (400)	$ (1,000)	(500)
Fiscal 2019 Acquisition
Business Acquisition [Line Items]
Aggregate purchase price partnership acquired			$ 1,200
Propane Dealers
Business Acquisition [Line Items]
Number of businesses acquired | PartnershipUnit		2