Business Combinations - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2013 PartnershipUnit	Sep. 30, 2012 PartnershipUnit	Sep. 30, 2011 PartnershipUnit
Redomestication [Line Items]
Number of heating oil dealer acquired	2	7	4
Aggregate purchase price partnership acquired	$ 1.4	$ 39.2	$ 9.7
Gross purchase price allocation, intangible assets	1.3	32.4	4.3
Gross purchase price allocation, fixed assets	0.2	8.0	3.5
Gross purchase price reduced by working capital credits	0.1	1.2
Gross purchase price allocation, working capital			$ 1.9