Inventories - Additional Information (Detail) - gal gal in Millions	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Inventory [Line Items]
Heating oil and other fuel inventories	21.7	14.3
Maximum product supply by other supplier	10.00%	10.00%
Home heating oil and Propane
Inventory [Line Items]
Market price based product supply contracts for next twelve months	283.8
Diesel and gasoline
Inventory [Line Items]
Market price based product supply contracts for next twelve months	21.7
Global Companies LLC
Inventory [Line Items]
Product purchases	12.00%	17.00%
Nic Holding Corp
Inventory [Line Items]
Product purchases	10.00%	11.00%