Goodwill and Other Intangible Assets - Carrying Values of Goodwill Assigned to Partnership's Operating Segments (Details) - USD ($) $ in Thousands		9 Months Ended
		Jun. 30, 2018	Sep. 30, 2017
Goodwill [Line Items]
Goodwill		$ 1,099,932	$ 1,101,097
Accumulated adjustments		(6,462)	(6,462)
Goodwill, net		1,093,470	1,094,635
Goodwill disposed	[1]	(1,165)
Propane [Member]
Goodwill [Line Items]
Goodwill		1,081,132	1,082,297
Accumulated adjustments		0	0
Goodwill, net		1,081,132	1,082,297
Goodwill disposed	[1]	(1,165)
Fuel Oil and Refined Fuels [Member]
Goodwill [Line Items]
Goodwill		10,900	10,900
Accumulated adjustments		(6,462)	(6,462)
Goodwill, net		4,438	4,438
Goodwill disposed	[1]	0
Natural Gas and Electricity [Member]
Goodwill [Line Items]
Goodwill		7,900	7,900
Accumulated adjustments		0	0
Goodwill, net		7,900	$ 7,900
Goodwill disposed	[1]	$ 0

[1] Reflects the impact from the disposition of certain assets and operations in a non-strategic market of the propane segment (Note 3).