Revenue Recognition - Summary of Disaggregation of Revenue by Major Sources (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Disaggregation Of Revenue [Line Items]
Total sales	$ 666,032	$ 737,617	$ 1,194,128	$ 1,385,804
Home heating oil and propane
Disaggregation Of Revenue [Line Items]
Total sales	508,155	566,457	859,369	1,001,980
Other petroleum products
Disaggregation Of Revenue [Line Items]
Total sales	87,143	102,755	184,479	237,161
Petroleum products
Disaggregation Of Revenue [Line Items]
Total sales	595,298	669,212	1,043,848	1,239,141
Equipment installations
Disaggregation Of Revenue [Line Items]
Total sales	26,224	25,208	60,539	57,997
Equipment maintenance service contracts
Disaggregation Of Revenue [Line Items]
Total sales	29,386	28,961	58,302	57,677
Billable call services
Disaggregation Of Revenue [Line Items]
Total sales	15,124	14,236	31,439	30,989
Installations and services
Disaggregation Of Revenue [Line Items]
Total sales	$ 70,734	$ 68,405	$ 150,280	$ 146,663