Business Combinations - Additional Information (Detail) (USD $)	12 Months Ended					0 Months Ended	12 Months Ended
	Sep. 30, 2014 PartnershipUnit	Sep. 30, 2013 PartnershipUnit	Sep. 30, 2012 PartnershipUnit	Sep. 30, 2014 Minimum	Sep. 30, 2014 Maximum	Mar. 04, 2014 Griffith Energy Services, Inc. Customer	Sep. 30, 2014 Griffith Energy Services, Inc.	Mar. 04, 2014 Griffith Energy Services, Inc.
Business Acquisition [Line Items]
Number of heating oil dealer acquired	3	2	7
Aggregate purchase price partnership acquired	$ 98,500,000	$ 1,400,000	$ 39,200,000
Gross purchase price allocation, intangible assets	53,700,000	1,300,000	32,400,000
Gross purchase price allocation, fixed assets	17,600,000	200,000	8,000,000					17,263,000
Gross purchase price reduced by working capital credits	27,200,000	100,000	1,200,000
Customer lists, other intangibles and trade names amortization period				7 years	20 years
Name of acquired entity							Griffith Energy Services, Inc.
Percentage of voting equity interests acquired								100.00%
Total Cash paid to acquire business	98,463,000	1,376,000	39,217,000			97,700,000
Cash paid to acquire business						69,900,000
Working capital acquired, net of cash								27,800,000
Cash acquired	4,151,000	0	0			4,200,000
Number of customers acquired from Griffith						50,000
Total costs related to the acquisition	1,000,000						800,000
Goodwill	209,331,000	201,130,000	201,103,000				8,200,000	8,168,000
Sales of acquired entity since acquisition date							139,100,000
Net (loss) of acquired entity since acquisition date							$ (3,000,000)