Revenue Recognition - Summary of Disaggregation of Revenue by Major Sources (Detail) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Disaggregation Of Revenue [Line Items]
Total sales	$ 488,063	$ 528,096
Home heating oil and propane
Disaggregation Of Revenue [Line Items]
Total sales	322,840	351,214
Other petroleum products
Disaggregation Of Revenue [Line Items]
Total sales	76,619	97,336
Petroleum products
Disaggregation Of Revenue [Line Items]
Total sales	399,459	448,550
Equipment installations
Disaggregation Of Revenue [Line Items]
Total sales	37,883	34,315
Equipment maintenance service contracts
Disaggregation Of Revenue [Line Items]
Total sales	30,955	28,916
Billable call services
Disaggregation Of Revenue [Line Items]
Total sales	19,766	16,315
Installations and services
Disaggregation Of Revenue [Line Items]
Total sales	$ 88,604	$ 79,546