Business Combinations - Additional Information (Detail) $ in Thousands	12 Months Ended
	Sep. 30, 2020 USD ($) PartnershipUnit	Sep. 30, 2019 USD ($) PartnershipUnit	Sep. 30, 2018 USD ($) PartnershipUnit
Heating Oil Dealers
Business Acquisition [Line Items]
Number of businesses acquired | PartnershipUnit	2		5
Aggregate purchase price partnership acquired	$ 3,300
Cash paid	3,000
Deferred liabilities	300
Aggregate purchase price allocation, intangible assets	3,200
Aggregate purchase price allocation, fixed assets	600
Gross purchase price increased (reduced) by working capital credits	(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
Motor Fuel Dealer
Business Acquisition [Line Items]
Number of businesses acquired | PartnershipUnit			1
Heating Oil Dealer and Motor Fuel Dealer
Business Acquisition [Line Items]
Aggregate purchase price partnership acquired			$ 25,200
Cash paid			23,700
Deferred liabilities			1,500
Aggregate purchase price allocation, intangible assets			15,300
Aggregate purchase price allocation, fixed assets			7,500
Gross purchase price increased (reduced) by working capital credits			$ 2,400