Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period			$ 4,137
Other comprehensive (loss) income before reclassification adjustments	$ 16	$ 20	27	$ 4
Amounts reclassified from AOCI	5	5	15	8
Other comprehensive income attributable to UGI	21	25	42	12
Balance, end of period	5,106	4,135	5,106	4,135
Postretirement Benefit Plans
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	(25)	(24)	(26)	(26)
Other comprehensive (loss) income before reclassification adjustments	0	0	0	0
Amounts reclassified from AOCI	0	0	1	2
Other comprehensive income attributable to UGI	0	0	1	2
Balance, end of period	(25)	(24)	(25)	(24)
Derivative Instruments
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	(41)	(54)	(54)	(25)
Other comprehensive (loss) income before reclassification adjustments	0	(8)	4	(38)
Amounts reclassified from AOCI	5	5	14	6
Other comprehensive income attributable to UGI	5	(3)	18	(32)
Balance, end of period	(36)	(57)	(36)	(57)
Foreign Currency
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	(60)	(152)	(67)	(166)
Other comprehensive (loss) income before reclassification adjustments	16	28	23	42
Amounts reclassified from AOCI	0	0	0	0
Other comprehensive income attributable to UGI	16	28	23	42
Balance, end of period	(44)	(124)	(44)	(124)
Total
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	(126)	(230)	(147)	(217)
Balance, end of period	$ (105)	$ (205)	$ (105)	$ (205)