Business Combinations - Additional Information (Detail) $ in Thousands		12 Months Ended
	Mar. 04, 2014 USD ($)	Sep. 30, 2015 USD ($) PartnershipUnit	Sep. 30, 2014 USD ($) PartnershipUnit	Sep. 30, 2013 USD ($) PartnershipUnit
Business Acquisition [Line Items]
Number of heating oil dealer acquired | PartnershipUnit		2	3	2
Aggregate purchase price partnership acquired		$ 21,100	$ 98,500	$ 1,400
Gross purchase price allocation, intangible assets		20,700	53,700	1,300
Gross purchase price allocation, fixed assets		2,500	17,600	200
Gross purchase price reduced by working capital credits		2,100	27,200	100
Total Cash paid to acquire business		21,130	98,463	1,376
Cash acquired		$ 0	$ 4,151	$ 0
Griffith Energy Services, Inc.
Business Acquisition [Line Items]
Gross purchase price allocation, fixed assets	$ 17,263
Name of acquired entity		Griffith Energy Services, Inc.
Percentage of voting equity interests acquired	100.00%
Total Cash paid to acquire business	$ 97,700
Cash paid to acquire business	69,900
Working capital acquired, net of cash	27,800
Cash acquired	$ 4,200
Minimum
Business Acquisition [Line Items]
Customer lists, other intangibles and trade names amortization period		7 years
Maximum
Business Acquisition [Line Items]
Customer lists, other intangibles and trade names amortization period		20 years