Segment Information - Reconciliation of Partnership Adjusted EBITDA (Details) - USD ($) $ in Millions	3 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions	$ 96	$ (27)
AmeriGas Propane \| Corporate & Other
Segment Reporting Information [Line Items]
Business transformation expenses	(12)	(11)
AmeriGas Propane \| Affiliated Entity \| CMG \| Pennant \| Corporate & Other
Segment Reporting Information [Line Items]
Acquisition and integration expenses associated with the CMG Acquisition		0
AmeriGas Propane \| Commodity contracts \| Corporate & Other
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions	0	0
AmeriGas Propane \| Cost of sales \| Corporate & Other
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions	37	9
AmeriGas Propane \| Foreign currency contracts \| Corporate & Other
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions	0	0
UGI International \| Corporate & Other
Segment Reporting Information [Line Items]
Business transformation expenses	(3)	(6)
UGI International \| Affiliated Entity \| CMG \| Pennant \| Corporate & Other
Segment Reporting Information [Line Items]
Acquisition and integration expenses associated with the CMG Acquisition		0
UGI International \| Commodity contracts \| Corporate & Other
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions	0	0
UGI International \| Cost of sales \| Corporate & Other
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions	106	(14)
UGI International \| Foreign currency contracts \| Corporate & Other
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions	(20)	(15)
Midstream & Marketing \| Corporate & Other
Segment Reporting Information [Line Items]
Business transformation expenses	0	0
Midstream & Marketing \| Affiliated Entity \| CMG \| Pennant \| Corporate & Other
Segment Reporting Information [Line Items]
Acquisition and integration expenses associated with the CMG Acquisition		(1)
Midstream & Marketing \| Commodity contracts \| Corporate & Other
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions	2	2
Midstream & Marketing \| Cost of sales \| Corporate & Other
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions	(29)	(9)
Midstream & Marketing \| Foreign currency contracts \| Corporate & Other
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions	$ 0	$ 0

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

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