Segment Information - Corporate and Other segment information (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions									$ 81	$ (259)	$ 133
Loss on extinguishments of debt				$ (4)					0	(6)
Loss on disposals of Conemaugh and HVAC									(54)	0	0
AmeriGas Merger expenses									0	0	(75)
Operating income (loss)	$ (69)	$ (174)	$ (362)	$ (377)	$ 99	$ (9)	$ (539)	$ (168)	(982)	(617)	(1,065)
AmeriGas Propane | Scenario, Adjustment
Segment Reporting Information [Line Items]
Operating income (loss)									113
UGI International | Scenario, Adjustment
Segment Reporting Information [Line Items]
Operating income (loss)									4
Midstream & Marketing | Scenario, Adjustment
Segment Reporting Information [Line Items]
Operating income (loss)									70
UGI Utilities | Scenario, Adjustment
Segment Reporting Information [Line Items]
Operating income (loss)									8
Corporate & Other
Segment Reporting Information [Line Items]
Loss on extinguishments of debt										(6)
Operating income (loss)									1	345	21
Corporate & Other | AmeriGas Propane
Segment Reporting Information [Line Items]
Loss on extinguishments of debt										0
LPG business transformation expenses									(44)	(15)
Loss on disposals of Conemaugh and HVAC									0
AmeriGas Merger expenses										(6)	(75)
Corporate & Other | UGI International
Segment Reporting Information [Line Items]
Loss on extinguishments of debt										(6)
LPG business transformation expenses									(18)	(9)
Loss on disposals of Conemaugh and HVAC									0
AmeriGas Merger expenses										0	0
Corporate & Other | Midstream & Marketing
Segment Reporting Information [Line Items]
Loss on extinguishments of debt										0
LPG business transformation expenses									0	0
Loss on disposals of Conemaugh and HVAC									(54)
AmeriGas Merger expenses										0	0
Commodity contracts | Corporate & Other | AmeriGas Propane | Revenues
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions									0	0	0
Commodity contracts | Corporate & Other | AmeriGas Propane | Cost of sales
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions									72	(117)	13
Commodity contracts | Corporate & Other | UGI International | Revenues
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions									0	0	0
Commodity contracts | Corporate & Other | UGI International | Cost of sales
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions									0	(143)	93
Commodity contracts | Corporate & Other | Midstream & Marketing | Revenues
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions									3	4	(4)
Commodity contracts | Corporate & Other | Midstream & Marketing | Cost of sales
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions									42	(35)	2
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
Foreign currency contracts | Corporate & Other | UGI International
Segment Reporting Information [Line Items]
Net gains on commodity derivative instruments not associated with current-period transactions									(36)	32	29
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
Trademarks and tradenames
Segment Reporting Information [Line Items]
AmeriGas Merger expenses		$ (37)
Affiliated Entity | CMG | Pennant | Corporate & Other | AmeriGas Propane
Segment Reporting Information [Line Items]
Acquisition and integration expenses associated with the CMG Acquisition									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
Affiliated Entity | CMG | Pennant | Corporate & Other | Midstream & Marketing
Segment Reporting Information [Line Items]
Acquisition and integration expenses associated with the CMG Acquisition									$ (2)	$ (16)
Affiliated Entity | Finagaz | Corporate & Other | AmeriGas Propane
Segment Reporting Information [Line Items]
Acquisition and integration expenses associated with the CMG Acquisition											0
Affiliated Entity | Finagaz | Corporate & Other | UGI International
Segment Reporting Information [Line Items]
Acquisition and integration expenses associated with the CMG Acquisition											(31)
Affiliated Entity | Finagaz | Corporate & Other | Midstream & Marketing
Segment Reporting Information [Line Items]
Acquisition and integration expenses associated with the CMG Acquisition											$ 0