Revenue Recognition - Summary of Disaggregation of Revenue by Major Sources (Detail) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disaggregation Of Revenue [Line Items]
Total sales	$ 373,320	$ 508,945
Home heating oil and propane
Disaggregation Of Revenue [Line Items]
Total sales	240,812	343,346
Other petroleum products
Disaggregation Of Revenue [Line Items]
Total sales	59,520	89,342
Petroleum products
Disaggregation Of Revenue [Line Items]
Total sales	300,332	432,688
Equipment installations
Disaggregation Of Revenue [Line Items]
Total sales	30,060	30,565
Equipment maintenance service contracts
Disaggregation Of Revenue [Line Items]
Total sales	26,868	27,908
Billable call services
Disaggregation Of Revenue [Line Items]
Total sales	16,060	17,784
Installations and services
Disaggregation Of Revenue [Line Items]
Total sales	$ 72,988	$ 76,257