Revenue Recognition - Summary of Disaggregation of Revenue by Major Sources (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Disaggregation Of Revenue [Line Items]
Total sales	$ 266,937	$ 300,121	$ 737,617	$ 648,187	$ 296,644	$ 439,101	$ 782,543	$ 488,270	$ 1,952,862	$ 2,006,558	$ 1,497,086
Home heating oil and propane
Disaggregation Of Revenue [Line Items]
Total sales									1,202,194	1,170,552	881,526
Motor fuel and other petroleum products
Disaggregation Of Revenue [Line Items]
Total sales									448,547	527,729	322,793
Petroleum products
Disaggregation Of Revenue [Line Items]
Total sales									1,650,741	1,698,281	1,204,319
Equipment installations
Disaggregation Of Revenue [Line Items]
Total sales									114,756	121,023	110,475
Equipment maintenance service contracts
Disaggregation Of Revenue [Line Items]
Total sales									126,887	121,623	118,546
Billable call services
Disaggregation Of Revenue [Line Items]
Total sales									60,478	65,631	63,746
Installations and services
Disaggregation Of Revenue [Line Items]
Total sales									$ 302,121	$ 308,277	$ 292,767