Inventories - Additional Information (Detail) - gal gal in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Inventory [Line Items]
Heating oil and other fuel inventories	10.1	8.4
Shell Oil Company
Inventory [Line Items]
Percentage of product purchases from supplier		16.00%
Motiva Enterprises LLC
Inventory [Line Items]
Percentage of product purchases from supplier	16.00%	15.00%
Global Companies LLC
Inventory [Line Items]
Percentage of product purchases from supplier	14.00%
Home heating oil and propane
Inventory [Line Items]
Market based product supply contracts for next twelve months	179.0
Diesel and gasoline
Inventory [Line Items]
Market based product supply contracts for next twelve months	56.0