Employee Retirement Plans - Change in Pension Benefits and Other Postretirement Benefits Obligations (Details) - Pension Benefits - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Change in benefit obligations:
Benefit obligations — beginning of year	$ 633	$ 870
Service cost	9	16	$ 12
Interest cost	35	26	22
Actuarial gain	(20)	(240)
Plan amendments	0	1
Foreign currency	2	(6)
Benefits paid	(36)	(34)
Benefit obligations — end of year	623	633	870
Change in plan assets:
Fair value of plan assets — beginning of year	541	736
Actual gain (loss) on plan assets	31	(173)
Foreign currency	1	(3)
Employer contributions	19	15
Benefits paid	(36)	(34)
Fair value of plan assets — end of year	556	541	$ 736
Funded status of the plans — end of year	(67)	(92)
Amounts recorded in UGI Corporation stockholders’ equity (pre-tax):
Prior service cost	3	3
Net actuarial gain	(17)	(17)
Total	(14)	(14)
Amounts recorded in regulatory assets and liabilities (pre-tax):
Net actuarial loss	110	114
Total	110	114
ABO for the pension plans	$ 558	$ 570