Segment Information - Schedule of Reconciliation of Partnership Adjusted EBITDA (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting Information [Line Items]
Unrealized gain (loss) on derivatives	$ (19)	$ (10)	$ (1,682)
Loss on extinguishments of debt	(10)	(9)	(9)
Loss associated with impairment of AmeriGas Propane goodwill	0	(195)	(656)
Loss on disposal of business	(36)	(95)	(221)
Midstream & Marketing
Segment Reporting Information [Line Items]
Loss on extinguishments of debt	0	(1)	0
Pre-tax impairment charge
Loss associated with impairment of AmeriGas Propane goodwill		0	0
Loss on disposal of business	0	(66)
Interest income from intersegment loan	0
AmeriGas operations enhancement for growth project		0	0
Restructuring costs		$ (1)
Restructuring Charges, Statement of Income or Comprehensive Income [Extensible Enumeration]		Operating and administrative expenses
UGI International
Segment Reporting Information [Line Items]
Loss on extinguishments of debt	0	$ 0	0
Pre-tax impairment charge		(33)
Loss associated with impairment of AmeriGas Propane goodwill		0	0
Loss on disposal of business	(53)	0
Interest income from intersegment loan	12
AmeriGas operations enhancement for growth project		0	0
Restructuring costs		$ (57)
Restructuring Charges, Statement of Income or Comprehensive Income [Extensible Enumeration]		Operating and administrative expenses
AmeriGas Propane
Segment Reporting Information [Line Items]
Loss on extinguishments of debt	(9)	$ (8)	(9)
Pre-tax impairment charge
Loss associated with impairment of AmeriGas Propane goodwill		(195)	(656)
Loss on disposal of business	17	0
Interest income from intersegment loan	0
AmeriGas operations enhancement for growth project		(25)	(24)
Restructuring costs		$ (1)
Restructuring Charges, Statement of Income or Comprehensive Income [Extensible Enumeration]		Operating and administrative expenses
Revenues | Midstream & Marketing
Segment Reporting Information [Line Items]
Unrealized gain (loss) on derivatives	(1)	$ 0	6
Business Exit Costs		0
Revenues | UGI International
Segment Reporting Information [Line Items]
Unrealized gain (loss) on derivatives	0	1	4
Business Exit Costs		(42)
Revenues | AmeriGas Propane
Segment Reporting Information [Line Items]
Unrealized gain (loss) on derivatives	0	0	0
Business Exit Costs		0
Cost of sales | Midstream & Marketing
Segment Reporting Information [Line Items]
Unrealized gain (loss) on derivatives	38	63	(236)
Cost of sales | UGI International
Segment Reporting Information [Line Items]
Unrealized gain (loss) on derivatives	(48)	(5)	(1,402)
Cost of sales | AmeriGas Propane
Segment Reporting Information [Line Items]
Unrealized gain (loss) on derivatives	1	21	(16)
Other operating expense (income), net | Midstream & Marketing
Segment Reporting Information [Line Items]
Unrealized gain (loss) on derivatives	0	0
Other operating expense (income), net | UGI International
Segment Reporting Information [Line Items]
Unrealized gain (loss) on derivatives	1	(3)
Other operating expense (income), net | AmeriGas Propane
Segment Reporting Information [Line Items]
Unrealized gain (loss) on derivatives	0	0
Other non-operating income (expense), net | Midstream & Marketing
Segment Reporting Information [Line Items]
Unrealized gain (loss) on derivatives	0	0	0
Other non-operating income (expense), net | UGI International
Segment Reporting Information [Line Items]
Unrealized gain (loss) on derivatives	(10)	(31)	(38)
Other non-operating income (expense), net | AmeriGas Propane
Segment Reporting Information [Line Items]
Unrealized gain (loss) on derivatives	$ 0	0	0
Operating and administrative expenses; Other operating expense (income), net | Midstream & Marketing
Segment Reporting Information [Line Items]
Business Exit Costs		0	0
Operating and administrative expenses; Other operating expense (income), net | UGI International
Segment Reporting Information [Line Items]
Business Exit Costs		(13)	(27)
Operating and administrative expenses; Other operating expense (income), net | AmeriGas Propane
Segment Reporting Information [Line Items]
Business Exit Costs		0	0
(Gain) loss on disposals of businesses | Midstream & Marketing
Segment Reporting Information [Line Items]
Business Exit Costs		0	0
(Gain) loss on disposals of businesses | UGI International
Segment Reporting Information [Line Items]
Business Exit Costs		(29)	(221)
(Gain) loss on disposals of businesses | AmeriGas Propane
Segment Reporting Information [Line Items]
Business Exit Costs		$ 0	$ 0