Segment Information - Schedule of Segment Reporting Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023	Sep. 30, 2023
Segment Reporting Information [Line Items]
Revenues	$ 2,467	$ 3,106	$ 4,588	$ 5,865
Cost of sales	1,030	2,148	2,232	5,254
Operating income (loss)	717	255	949	(949)
Income (loss) from equity investees	1	0	2	1
Other non-operating (expense) income, net	11	2	(2)	(26)
Earnings before interest expense and income taxes	729	257	949	(974)
Interest expense	(100)	(93)	(200)	(185)
Income (loss) before income taxes	629	164	749	(1,159)
Depreciation and amortization	138	132	275	263
Capital expenditures (including the effects of accruals)	167	214	300	392
Total assets	15,624	16,429	15,624	16,429	$ 15,401
Eliminations
Segment Reporting Information [Line Items]
Revenues	(131)	(128)	(211)	(277)
Cost of sales	(131)	(126)	(211)	(275)
Operating income (loss)	1	(1)	0	0
Income (loss) from equity investees	0	0	0	0
Other non-operating (expense) income, net	0	0	0	0
Earnings before interest expense and income taxes	1	(1)	0	0
Interest expense	0	0	0	0
Income (loss) before income taxes	1	(1)	0	0
Depreciation and amortization	0	0	0	0
Capital expenditures (including the effects of accruals)	0	0	0	0
Total assets	(131)	(232)	(131)	(232)
Eliminations | Utilities
Segment Reporting Information [Line Items]
Revenues	23	28	36	61
Eliminations | Midstream & Marketing
Segment Reporting Information [Line Items]
Revenues	108	98	175	213
Eliminations | UGI International
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Eliminations | AmeriGas Propane
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Operating Segments | Utilities
Segment Reporting Information [Line Items]
Revenues	646	774	1,139	1,366
Revenues from external customers	623	746	1,103	1,305
Cost of sales	274	426	495	755
Operating income (loss)	225	203	359	329
Income (loss) from equity investees	0	0	0	0
Other non-operating (expense) income, net	1	2	2	4
Earnings before interest expense and income taxes	226	205	361	333
Interest expense	(24)	(21)	(47)	(42)
Income (loss) before income taxes	202	184	314	291
Depreciation and amortization	41	37	82	74
Capital expenditures (including the effects of accruals)	91	133	173	250
Total assets	5,850	5,643	5,850	5,643
Operating Segments | Midstream & Marketing
Segment Reporting Information [Line Items]
Revenues	483	638	877	1,307
Revenues from external customers	375	540	702	1,094
Cost of sales	283	479	522	993
Operating income (loss)	151	103	250	209
Income (loss) from equity investees	2	2	5	3
Other non-operating (expense) income, net	0	0	0	0
Earnings before interest expense and income taxes	153	105	255	212
Interest expense	(9)	(11)	(20)	(22)
Income (loss) before income taxes	144	94	235	190
Depreciation and amortization	22	22	44	43
Capital expenditures (including the effects of accruals)	33	23	52	34
Total assets	3,204	3,116	3,204	3,116
Operating Segments | UGI International
Segment Reporting Information [Line Items]
Revenues	673	948	1,398	1,825
Cost of sales	368	633	814	1,295
Operating income (loss)	124	120	237	176
Income (loss) from equity investees	(1)	(2)	(3)	(2)
Other non-operating (expense) income, net	8	10	14	20
Earnings before interest expense and income taxes	131	128	248	194
Interest expense	(11)	(9)	(22)	(16)
Income (loss) before income taxes	120	119	226	178
Depreciation and amortization	29	28	59	56
Capital expenditures (including the effects of accruals)	19	30	31	57
Total assets	3,030	3,490	3,030	3,490
Operating Segments | AmeriGas Propane
Segment Reporting Information [Line Items]
Revenues	795	867	1,424	1,633
Cost of sales	362	430	645	816
Operating income (loss)	138	138	209	248
Income (loss) from equity investees	0	0	0	0
Other non-operating (expense) income, net	0	0	0	0
Earnings before interest expense and income taxes	138	138	209	248
Interest expense	(40)	(39)	(81)	(82)
Income (loss) before income taxes	98	99	128	166
Depreciation and amortization	44	45	88	89
Capital expenditures (including the effects of accruals)	24	28	44	51
Total assets	3,467	4,248	3,467	4,248
Corporate & Other
Segment Reporting Information [Line Items]
Revenues from external customers	1	5	(39)	8
Cost of sales	(126)	306	(33)	1,670
Operating income (loss)	78	(308)	(106)	(1,911)
Income (loss) from equity investees	0	0	0	0
Other non-operating (expense) income, net	2	(10)	(18)	(50)
Earnings before interest expense and income taxes	80	(318)	(124)	(1,961)
Interest expense	(16)	(13)	(30)	(23)
Income (loss) before income taxes	64	(331)	(154)	(1,984)
Depreciation and amortization	2	0	2	1
Capital expenditures (including the effects of accruals)	0	0	0	0
Total assets	204	164	204	164
Intersegment revenues Corporate & Other
Segment Reporting Information [Line Items]
Revenues	$ 0	$ 2	$ 0	$ 3