Segment Information - Reconciliation of Partnership Adjusted EBITDA (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Depreciation and amortization	$ (118.8)	$ (104.1)	$ (341.3)	$ (301.5)
Interest expense	(56.5)	(56.8)	(172.8)	(168.0)
Impairment of tradenames	(75.0)	0.0	(75.0)	0.0
Loss on extinguishments of debt	0.0	(4.4)	0.0	(59.7)
(Loss) income before income taxes	(1.1)	(79.3)	$ 849.8	735.8
Cost-method Investments, other than temporary impairment				7.0
Amerigas Propane \| AmeriGas OLP
Segment Reporting Information [Line Items]
General Partnership interest (percentage)			1.01%
Corporate & Other
Segment Reporting Information [Line Items]
Depreciation and amortization	(0.2)	(0.2)	$ (0.7)	(0.7)
Interest expense	(0.1)	(0.1)	(0.4)	(0.1)
Loss on extinguishments of debt		0.0		0.0
(Loss) income before income taxes	89.2	(54.6)	37.0	15.1
Gains (losses) on unsettled commodity derivative instruments, net	95.5	(52.7)	54.0	28.9
Operating Segments \| Amerigas Propane
Segment Reporting Information [Line Items]
Partnership Adjusted EBITDA	67.2	58.4	570.8	514.7
Depreciation and amortization	(46.4)	(46.2)	(139.0)	(135.8)
Interest expense	(40.4)	(40.6)	(122.0)	(120.6)
Impairment of tradenames	(75.0)	0.0	(75.0)	0.0
Loss on extinguishments of debt	0.0	(4.4)	0.0	(59.7)
MGP environmental remediation accrual	0.0	(7.5)	0.0	(7.5)
Noncontrolling interest	(0.5)	(0.1)	3.0	2.4
(Loss) income before income taxes	$ (95.1)	$ (40.4)	$ 237.8	$ 193.5

Gains (Losses) On Unsettled Commodity Derivative Instruments, Net

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Non-controlling interests representing general partners interest in OLP.

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Amount of expense for newly incurred environmental loss contingencies. Includes, but is not limited to, remediation expense and interest accretion.

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Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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Amount of impairment loss resulting from write-down of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit to fair value.

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Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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Interest and debt related expenses associated with nonoperating financing activities of the entity.

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Percentage investment held by the managing member or general partner of the limited liability company (LLC) or limited partnership (LP).

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