Goodwill and Other Intangible Assets - Summary of Other Intangible Assets (Details) - USD ($) $ in Thousands		Jun. 30, 2018	Sep. 30, 2017
Finite Lived Intangible Assets [Line Items]
Other intangible assets, gross		$ 534,940	$ 525,663
Accumulated amortization		(345,558)	(305,787)
Other intangible assets, net		189,382	219,876
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Other intangible assets, gross	[1],[2]	499,433	492,656
Accumulated amortization		(317,024)	(279,287)
Non-compete Agreements [Member]
Finite Lived Intangible Assets [Line Items]
Other intangible assets, gross	[1]	33,540	31,040
Accumulated amortization		(27,207)	(25,242)
Other [Member]
Finite Lived Intangible Assets [Line Items]
Other intangible assets, gross		1,967	1,967
Accumulated amortization		$ (1,327)	$ (1,258)

[1] Reflects the impact from the acquisitions (Note 3).

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