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Segment Information - Reconciliation of Partnership Adjusted EBITDA (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions			$ 1.1	$ (200.7)
Impairment of assets held-for-sale	$ (51.6)	$ 0.0	(51.6)	0.0
Loss on extinguishments of debt	0.0	0.0	0.0	(6.1)
Corporate & Other
Segment Reporting Information [Line Items]
Loss on extinguishments of debt				(6.1)
Corporate & Other \| AmeriGas Propane
Segment Reporting Information [Line Items]
LPG business transformation expenses	(2.7)		(26.7)
Impairment of assets held-for-sale	0.0		0.0
AmeriGas Merger expenses		(1.8)		(2.7)
Loss on extinguishments of debt				0.0
Corporate & Other \| UGI International
Segment Reporting Information [Line Items]
LPG business transformation expenses	(3.7)		(15.9)
Impairment of assets held-for-sale	0.0		0.0
AmeriGas Merger expenses		0.0		0.0
Loss on extinguishments of debt				(6.1)
Corporate & Other \| Midstream & Marketing
Segment Reporting Information [Line Items]
LPG business transformation expenses	0.0		0.0
Impairment of assets held-for-sale	(51.6)		(51.6)
AmeriGas Merger expenses		0.0		0.0
Loss on extinguishments of debt				0.0
Commodity contracts \| Corporate & Other \| AmeriGas Propane
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions	59.9	(3.4)	48.2	(64.8)
Commodity contracts \| Corporate & Other \| UGI International
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions	77.8	(10.8)	(53.8)	(136.7)
Commodity contracts \| Corporate & Other \| Midstream & Marketing
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions	24.8	(24.5)	26.8	(11.1)
Foreign currency contracts \| Corporate & Other \| AmeriGas Propane
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions	0.0	0.0	0.0	0.0
Foreign currency contracts \| Corporate & Other \| UGI International
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions	(6.8)	(0.8)	(20.1)	11.9
Foreign currency contracts \| Corporate & Other \| Midstream & Marketing
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions	0.0	$ 0.0	0.0	$ 0.0
Affiliated Entity \| CMG \| Pennant \| Corporate & Other \| AmeriGas Propane
Segment Reporting Information [Line Items]
Acquisition and integration expenses associated with the CMG Acquisition	0.0		0.0
Affiliated Entity \| CMG \| Pennant \| Corporate & Other \| UGI International
Segment Reporting Information [Line Items]
Acquisition and integration expenses associated with the CMG Acquisition	0.0		0.0
Affiliated Entity \| CMG \| Pennant \| Corporate & Other \| Midstream & Marketing
Segment Reporting Information [Line Items]
Acquisition and integration expenses associated with the CMG Acquisition	$ (0.2)		$ (1.9)