Revenue Recognition - Summary of Disaggregation of Revenue by Major Sources (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation Of Revenue [Line Items]
Total sales	$ 232,155	$ 283,376	$ 1,284,163	$ 1,517,985
Home heating oil and propane
Disaggregation Of Revenue [Line Items]
Total sales	120,951	115,988	877,763	1,034,554
Other petroleum products
Disaggregation Of Revenue [Line Items]
Total sales	44,231	94,669	201,382	272,210
Petroleum products
Disaggregation Of Revenue [Line Items]
Total sales	165,182	210,657	1,079,145	1,306,764
Equipment installations
Disaggregation Of Revenue [Line Items]
Total sales	21,548	24,344	72,271	74,711
Equipment maintenance service contracts
Disaggregation Of Revenue [Line Items]
Total sales	32,541	32,279	88,213	87,276
Billable call services
Disaggregation Of Revenue [Line Items]
Total sales	12,884	16,096	44,534	49,234
Installations and services
Disaggregation Of Revenue [Line Items]
Total sales	$ 66,973	$ 72,719	$ 205,018	$ 211,221