Employee Retirement Plans - Schedule of Change in Pension Benefits and Other Postretirement Benefits Obligations (Details) - Pension Benefits - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Change in benefit obligations:
Benefit obligations — beginning of year	$ 707	$ 623
Service cost	9	8	$ 9
Interest cost	34	36	35
Actuarial loss (gain)	(21)	76
Curtailments	(1)	0
Foreign currency	2	2
Benefits paid	(38)	(38)
Benefit obligations — end of year	692	707	623
Change in plan assets:
Fair value of plan assets — beginning of year	657	556
Actual gain (loss) on plan assets	44	118
Foreign currency	1	1
Employer contributions	15	19
Benefits paid	(38)	(37)
Fair value of plan assets — end of year	679	657	$ 556
Funded status of the plans — end of year	(13)	(50)
Amounts recorded in UGI Corporation stockholders’ equity (pre-tax):
Prior service cost	3	3
Net actuarial loss (gain)	(26)	(9)
Total	(23)	(6)
Amounts recorded in regulatory assets and liabilities (pre-tax):
Net actuarial loss (gain)	100	106
Total	100	106
ABO for the pension plans	$ 620	$ 633