Revenue Recognition - Summary of Disaggregation of Revenue by Major Sources (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Disaggregation Of Revenue [Line Items]
Total sales	$ 331,640	$ 300,121	$ 1,525,768	$ 1,685,925
Home heating oil and propane
Disaggregation Of Revenue [Line Items]
Total sales	155,161	122,003	1,014,530	1,123,983
Other petroleum products
Disaggregation Of Revenue [Line Items]
Total sales	93,840	101,562	278,319	338,723
Petroleum products
Disaggregation Of Revenue [Line Items]
Total sales	249,001	223,565	1,292,849	1,462,706
Equipment installations
Disaggregation Of Revenue [Line Items]
Total sales	30,143	27,474	90,682	85,471
Equipment maintenance service contracts
Disaggregation Of Revenue [Line Items]
Total sales	35,164	34,564	93,466	92,241
Billable call services
Disaggregation Of Revenue [Line Items]
Total sales	17,332	14,518	48,771	45,507
Installations and services
Disaggregation Of Revenue [Line Items]
Total sales	$ 82,639	$ 76,556	$ 232,919	$ 223,219