Segment Information - Schedule of Segment Reporting Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020	Sep. 30, 2020
Segment Reporting Information [Line Items]
Revenues	$ 2,581	$ 2,229	$ 4,513	$ 4,236
Cost of sales	1,274	1,248	2,107	2,256
Operating income	671	362	1,173	739
Income from equity investees	10	8	17	15
Other non-operating income (expense), net	18	12	(1)	0
Earnings before interest expense and income taxes	699	382	1,189	754
Interest expense	(78)	(83)	(156)	(167)
Income before income taxes	621	299	1,033	587
Depreciation and amortization	126	121	250	240
Capital expenditures (including the effects of accruals)	124	158	276	311
Total assets	14,945	14,136	14,945	14,136	$ 13,985
Eliminations
Segment Reporting Information [Line Items]
Revenues	(118)	(94)	(196)	(174)
Cost of sales	(117)	(94)	(194)	(173)
Operating income	0	0	0	0
Income from equity investees	0	0	0	0
Other non-operating income (expense), net	0	0	0	0
Earnings before interest expense and income taxes	0	0	0	0
Interest expense	0	0	0	0
Income before income taxes	0	0	0	0
Depreciation and amortization	0	0	0	0
Capital expenditures (including the effects of accruals)	0	0	0	0
Total assets	(227)	(370)	(227)	(370)
Eliminations | AmeriGas Propane
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Eliminations | UGI International
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Eliminations | Midstream & Marketing
Segment Reporting Information [Line Items]
Revenues	92	78	154	142
Eliminations | UGI Utilities
Segment Reporting Information [Line Items]
Revenues	25	16	40	31
Operating Segments | AmeriGas Propane
Segment Reporting Information [Line Items]
Revenues	940	802	1,606	1,532
Cost of sales	431	325	703	614
Operating income	239	206	380	371
Income from equity investees	0	0	0	0
Other non-operating income (expense), net	0	0	0	0
Earnings before interest expense and income taxes	239	206	380	371
Interest expense	(40)	(41)	(80)	(83)
Income before income taxes	199	165	300	288
Depreciation and amortization	44	45	87	89
Capital expenditures (including the effects of accruals)	30	35	57	74
Total assets	4,515	4,509	4,515	4,509
Operating Segments | UGI International
Segment Reporting Information [Line Items]
Revenues	834	704	1,534	1,355
Cost of sales	491	402	874	770
Operating income	147	117	282	213
Income from equity investees	0	0	0	0
Other non-operating income (expense), net	2	9	3	13
Earnings before interest expense and income taxes	149	126	285	226
Interest expense	(6)	(8)	(13)	(15)
Income before income taxes	143	118	272	211
Depreciation and amortization	34	31	67	62
Capital expenditures (including the effects of accruals)	18	22	47	42
Total assets	3,576	3,227	3,576	3,227
Operating Segments | Midstream & Marketing
Segment Reporting Information [Line Items]
Revenues	484	422	825	795
Revenues, before intersegment effect	392	344	671	653
Cost of sales	343	299	580	563
Operating income	90	71	142	126
Income from equity investees	10	8	17	15
Other non-operating income (expense), net	0	0	0	0
Earnings before interest expense and income taxes	100	79	159	141
Interest expense	(11)	(11)	(21)	(23)
Income before income taxes	89	68	138	118
Depreciation and amortization	19	19	37	37
Capital expenditures (including the effects of accruals)	12	23	29	46
Total assets	2,893	2,824	2,893	2,824
Operating Segments | UGI Utilities
Segment Reporting Information [Line Items]
Revenues	442	393	742	722
Revenues, before intersegment effect	417	377	702	691
Cost of sales	202	185	334	336
Operating income	142	116	219	208
Income from equity investees	0	0	0	0
Other non-operating income (expense), net	0	0	1	0
Earnings before interest expense and income taxes	142	116	220	208
Interest expense	(14)	(13)	(28)	(27)
Income before income taxes	128	103	192	181
Depreciation and amortization	29	26	58	52
Capital expenditures (including the effects of accruals)	64	78	143	149
Total assets	3,982	3,730	3,982	3,730
Corporate & Other
Segment Reporting Information [Line Items]
Revenues, before intersegment effect	(2)	2	0	5
Cost of sales	(76)	131	(190)	146
Operating income	53	(148)	150	(179)
Income from equity investees	0	0	0	0
Other non-operating income (expense), net	16	3	(5)	(13)
Earnings before interest expense and income taxes	69	(145)	145	(192)
Interest expense	(7)	(10)	(14)	(19)
Income before income taxes	62	(155)	131	(211)
Depreciation and amortization	0	0	1	0
Capital expenditures (including the effects of accruals)	0	0	0	0
Total assets	206	216	206	216
Intersegment revenues Corporate & Other
Segment Reporting Information [Line Items]
Revenues	$ 1	$ 0	$ 2	$ 1