Segment Information - Reconciliation of Partnership Adjusted EBITDA (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Depreciation and amortization	$ (112.2)	$ (99.3)	$ (222.5)	$ (197.4)
Interest expense	(58.1)	(55.8)	(116.3)	(111.2)
Loss on extinguishments of debt	0.0	(22.1)	0.0	(55.3)
Income (loss) before income taxes	521.1	436.4	$ 850.9	$ 815.1
Amerigas Propane | AmeriGas OLP
Segment Reporting Information [Line Items]
General Partnership interest (percentage)			1.01%	1.01%
Operating Segments | Amerigas Propane
Segment Reporting Information [Line Items]
Partnership Adjusted EBITDA	309.5	271.2	$ 503.6	$ 456.3
Depreciation and amortization	(45.2)	(45.0)	(92.6)	(89.6)
Interest expense	(41.0)	(40.0)	(81.6)	(80.0)
Loss on extinguishments of debt	0.0	(22.1)	0.0	(55.3)
Noncontrolling interest	2.3	1.1	3.5	2.5
Income (loss) before income taxes	$ 225.6	$ 165.2	$ 332.9	$ 233.9