Employee Retirement Plans - Change in Pension Benefits and Other Postretirement Benefits Obligations (Details) - Pension Benefits - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Change in benefit obligations:
Benefit obligations — beginning of year	$ 623	$ 633
Service cost	8	9	$ 16
Interest cost	36	35	26
Actuarial loss (gain)	76	(20)
Foreign currency	2	2
Benefits paid	(38)	(36)
Benefit obligations — end of year	707	623	633
Change in plan assets:
Fair value of plan assets — beginning of year	556	541
Actual gain (loss) on plan assets	118	31
Foreign currency	1	1
Employer contributions	19	19
Benefits paid	(37)	(36)
Fair value of plan assets — end of year	657	556	$ 541
Funded status of the plans — end of year	(50)	(67)
Amounts recorded in UGI Corporation stockholders’ equity (pre-tax):
Prior service cost	3	3
Net actuarial gain	(9)	(17)
Total	(6)	(14)
Amounts recorded in regulatory assets and liabilities (pre-tax):
Net actuarial loss	106	110
Total	106	110
ABO for the pension plans	$ 633	$ 558