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Segment Information - Reconciliation of Partnership Adjusted EBITDA (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Net gains (losses) on commodity derivative instruments not associated with current-period transactions			$ 509	$ 1
Impairment of assets held-for-sale	$ 0	$ (52)	0	(52)
AmeriGas Propane \| Revenues
Segment Reporting Information [Line Items]
Net gains (losses) on commodity derivative instruments not associated with current-period transactions	0	0	0	0
AmeriGas Propane \| Cost of sales
Segment Reporting Information [Line Items]
Net gains (losses) on commodity derivative instruments not associated with current-period transactions	59	60	123	48
AmeriGas Propane \| Other non-operating income (expense), net
Segment Reporting Information [Line Items]
Net gains (losses) on commodity derivative instruments not associated with current-period transactions	0	0	0	0
AmeriGas Propane \| Operating and administrative expenses
Segment Reporting Information [Line Items]
Business transformation expenses	(11)	(3)	(37)	(27)
AmeriGas Propane \| Operating and administrative expenses \| CMG Acquisition
Segment Reporting Information [Line Items]
Acquisition and integration expenses associated with the CMG Acquisition				0
AmeriGas Propane \| Impairment of assets held-for-sale
Segment Reporting Information [Line Items]
Impairment of assets held-for-sale		0		0
AmeriGas Propane \| (Loss) income from equity investees
Segment Reporting Information [Line Items]
Impairment of investment in PennEast	0		0
UGI International \| Revenues
Segment Reporting Information [Line Items]
Net gains (losses) on commodity derivative instruments not associated with current-period transactions	0	0	0	0
UGI International \| Cost of sales
Segment Reporting Information [Line Items]
Net gains (losses) on commodity derivative instruments not associated with current-period transactions	226	78	380	(54)
UGI International \| Other non-operating income (expense), net
Segment Reporting Information [Line Items]
Net gains (losses) on commodity derivative instruments not associated with current-period transactions	(1)	(7)	(6)	(20)
UGI International \| Operating and administrative expenses
Segment Reporting Information [Line Items]
Business transformation expenses	(6)	(4)	(12)	(16)
UGI International \| Operating and administrative expenses \| CMG Acquisition
Segment Reporting Information [Line Items]
Acquisition and integration expenses associated with the CMG Acquisition				0
UGI International \| Impairment of assets held-for-sale
Segment Reporting Information [Line Items]
Impairment of assets held-for-sale		0		0
UGI International \| (Loss) income from equity investees
Segment Reporting Information [Line Items]
Impairment of investment in PennEast	0		0
Midstream & Marketing \| Revenues
Segment Reporting Information [Line Items]
Net gains (losses) on commodity derivative instruments not associated with current-period transactions	(4)	3	(4)	8
Midstream & Marketing \| Cost of sales
Segment Reporting Information [Line Items]
Net gains (losses) on commodity derivative instruments not associated with current-period transactions	44	22	16	19
Midstream & Marketing \| Other non-operating income (expense), net
Segment Reporting Information [Line Items]
Net gains (losses) on commodity derivative instruments not associated with current-period transactions	0	0	0	0
Midstream & Marketing \| Operating and administrative expenses
Segment Reporting Information [Line Items]
Business transformation expenses	0	0	0	0
Midstream & Marketing \| Operating and administrative expenses \| CMG Acquisition
Segment Reporting Information [Line Items]
Acquisition and integration expenses associated with the CMG Acquisition				(2)
Midstream & Marketing \| Impairment of assets held-for-sale
Segment Reporting Information [Line Items]
Impairment of assets held-for-sale		$ (52)		$ (52)
Midstream & Marketing \| (Loss) income from equity investees
Segment Reporting Information [Line Items]
Impairment of investment in PennEast	$ 93		$ 93