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Segment Information - Corporate and Other segment information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Net (losses) gains on commodity derivative instruments not associated with current-period transactions			$ (154.6)	$ (161.2)
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	(12.8)		(24.0)
AmeriGas Merger expenses		(0.9)		(0.9)
Loss on extinguishments of debt				0.0
Corporate & Other \| UGI International
Segment Reporting Information [Line Items]
LPG business transformation expenses	(6.7)		(12.2)
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
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 (losses) gains on commodity derivative instruments not associated with current-period transactions	(21.1)	17.1	(11.7)	(61.4)
Commodity contracts \| Corporate & Other \| UGI International
Segment Reporting Information [Line Items]
Net (losses) gains on commodity derivative instruments not associated with current-period transactions	(118.1)	(28.6)	(131.6)	(125.9)
Commodity contracts \| Corporate & Other \| Midstream & Marketing
Segment Reporting Information [Line Items]
Net (losses) gains on commodity derivative instruments not associated with current-period transactions	9.5	11.6	2.0	13.4
Forward foreign currency exchange contracts \| Corporate & Other \| AmeriGas Propane
Segment Reporting Information [Line Items]
Net (losses) gains on commodity derivative instruments not associated with current-period transactions	0.0	0.0	0.0	0.0
Forward foreign currency exchange contracts \| Corporate & Other \| UGI International
Segment Reporting Information [Line Items]
Net (losses) gains on commodity derivative instruments not associated with current-period transactions	2.4	4.6	(13.3)	12.7
Forward foreign currency exchange contracts \| Corporate & Other \| Midstream & Marketing
Segment Reporting Information [Line Items]
Net (losses) 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	$ (1.0)		$ (1.7)