Business Combinations - Additional Information (Detail) $ in Thousands	12 Months Ended
	Sep. 30, 2021 USD ($) PartnershipUnit	Sep. 30, 2020 USD ($) PartnershipUnit	Sep. 30, 2019 USD ($) PartnershipUnit
Heating Oil Dealers
Business Acquisition [Line Items]
Number of businesses acquired | PartnershipUnit	3	2
Aggregate purchase price partnership acquired	$ 42,500	$ 3,300
Cash paid	40,700	3,000
Deferred liabilities	1,800	300
Aggregate purchase price allocation, goodwill and intangible assets	37,300	3,200
Aggregate purchase price allocation, fixed assets	6,200	600
Gross purchase price increased (reduced) by working capital credits	(1,000)	$ 500
Fiscal 2019 Acquisition
Business Acquisition [Line Items]
Aggregate purchase price partnership acquired	$ 1,200
Liquid Product Dealers
Business Acquisition [Line Items]
Number of businesses acquired | PartnershipUnit			1
Acquired Business
Business Acquisition [Line Items]
Aggregate purchase price partnership acquired			$ 60,904
Aggregate purchase price allocation, fixed assets			$ 14,926