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Segment Information - Corporate and Other segment information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Net gains (losses) on commodity derivative instruments not associated with current-period transactions	$ 1,398	$ 81	$ (259)
Loss on extinguishments of debt	0	0	(6)
Loss on disposals of Conemaugh and HVAC	0	(54)	0
Corporate & Other
Segment Reporting Information [Line Items]
Loss on extinguishments of debt			(6)
Corporate & Other \| AmeriGas Propane
Segment Reporting Information [Line Items]
Loss on extinguishments of debt			0
Loss on disposals of Conemaugh and HVAC		0
Corporate & Other \| AmeriGas Propane \| Revenues
Segment Reporting Information [Line Items]
Net gains (losses) on commodity derivative instruments not associated with current-period transactions	0	0	0
Corporate & Other \| AmeriGas Propane \| Cost of sales
Segment Reporting Information [Line Items]
Net gains (losses) on commodity derivative instruments not associated with current-period transactions	167	72	(117)
Corporate & Other \| AmeriGas Propane \| Other non-operating (expense) income, net
Segment Reporting Information [Line Items]
Net gains (losses) on commodity derivative instruments not associated with current-period transactions	0	0	0
Corporate & Other \| AmeriGas Propane \| Operating and administrative expenses
Segment Reporting Information [Line Items]
AmeriGas Merger expenses			(6)
Acquisition and integration expenses associated with the CMG Acquisition		0	0
Business transformation expenses	(54)	(44)	(15)
Impairment of customer relationship intangible	0
Corporate & Other \| AmeriGas Propane \| (Loss) income from equity method investees
Segment Reporting Information [Line Items]
Impairment of investment in PennEast	0
Corporate & Other \| UGI International
Segment Reporting Information [Line Items]
Loss on extinguishments of debt			(6)
Loss on disposals of Conemaugh and HVAC		0
Corporate & Other \| UGI International \| Revenues
Segment Reporting Information [Line Items]
Net gains (losses) on commodity derivative instruments not associated with current-period transactions	0	0	0
Corporate & Other \| UGI International \| Cost of sales
Segment Reporting Information [Line Items]
Net gains (losses) on commodity derivative instruments not associated with current-period transactions	1,065	0	(143)
Corporate & Other \| UGI International \| Other non-operating (expense) income, net
Segment Reporting Information [Line Items]
Net gains (losses) on commodity derivative instruments not associated with current-period transactions	8	(36)	32
Corporate & Other \| UGI International \| Operating and administrative expenses
Segment Reporting Information [Line Items]
AmeriGas Merger expenses			0
Acquisition and integration expenses associated with the CMG Acquisition		0	0
Business transformation expenses	(33)	(18)	(9)
Impairment of customer relationship intangible	(20)
Corporate & Other \| UGI International \| (Loss) income from equity method investees
Segment Reporting Information [Line Items]
Impairment of investment in PennEast	0
Corporate & Other \| Midstream & Marketing
Segment Reporting Information [Line Items]
Loss on extinguishments of debt			0
Loss on disposals of Conemaugh and HVAC		(54)
Corporate & Other \| Midstream & Marketing \| Revenues
Segment Reporting Information [Line Items]
Net gains (losses) on commodity derivative instruments not associated with current-period transactions	(15)	3	4
Corporate & Other \| Midstream & Marketing \| Cost of sales
Segment Reporting Information [Line Items]
Net gains (losses) on commodity derivative instruments not associated with current-period transactions	173	42	(35)
Corporate & Other \| Midstream & Marketing \| Other non-operating (expense) income, net
Segment Reporting Information [Line Items]
Net gains (losses) on commodity derivative instruments not associated with current-period transactions	0	0	0
Corporate & Other \| Midstream & Marketing \| Operating and administrative expenses
Segment Reporting Information [Line Items]
AmeriGas Merger expenses			0
Acquisition and integration expenses associated with the CMG Acquisition		(2)	(16)
Business transformation expenses	0	$ 0	$ 0
Impairment of customer relationship intangible	0
Corporate & Other \| Midstream & Marketing \| (Loss) income from equity method investees
Segment Reporting Information [Line Items]
Impairment of investment in PennEast	$ (93)