Segment Information - Reconciliation of Partnership Adjusted EBITDA (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Depreciation and amortization	$ (109.9)	$ (118.8)	$ (330.0)	$ (341.3)
Interest expense	(60.5)	(56.5)	(181.7)	(172.8)
Impairment of Partnership tradenames and trademarks	0.0	(75.0)	0.0	(75.0)
(Loss) income before income taxes	(48.7)	(1.1)	$ 550.5	849.8
AmeriGas Propane | AmeriGas OLP
Segment Reporting Information [Line Items]
General partnership interest (percentage)			1.01%
Operating Segments | AmeriGas Propane
Segment Reporting Information [Line Items]
Partnership Adjusted EBITDA	42.5	67.2	$ 543.5	570.8
Depreciation and amortization	(44.0)	(46.4)	(134.0)	(139.0)
Interest expense	(41.6)	(40.4)	(126.2)	(122.0)
Impairment of Partnership tradenames and trademarks	0.0	(75.0)	0.0	(75.0)
Merger expense	(1.8)	0.0	(2.7)	0.0
Noncontrolling interest	0.3	(0.5)	3.2	3.0
(Loss) income before income taxes	(44.6)	(95.1)	283.8	237.8
Corporate & Other
Segment Reporting Information [Line Items]
Depreciation and amortization	(0.3)	(0.2)	(0.7)	(0.7)
Interest expense	0.0	(0.1)	(0.2)	(0.4)
(Loss) income before income taxes	(39.2)	89.2	(208.1)	37.0
Gains (losses) on unsettled commodity derivative instruments, net	$ (39.5)	$ 95.5	$ (200.7)	$ 54.0