Common Stock and Equity-Based Compensation - Stock Option Awards (Details) - UGI Stock Option Awards - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Shares
Shares under option - beginning balance (in shares)	8,478,105	8,197,069	8,781,748
Granted (in shares)	1,893,700	1,197,100	1,401,400
Canceled (in shares)	(57,668)	(123,012)	(152,017)
Expired (in shares)	(93,728)	(13,699)	(1,666)
Exercised (in shares)	(230,875)	(779,353)	(1,832,396)
Shares under option - ending balance (in shares)	9,989,534	8,478,105	8,197,069	8,781,748
Weighted - Average Option Price
Shares under option - beginning balance (in dollars per share)	$ 37.18	$ 33.93	$ 30.20
Granted (in dollars per share)	43.20	53.27	47.85
Canceled (in dollars per share)	49.69	48.69	42.14
Expired (in dollars per share)	37.81	47.49	35.80
Exercised (in dollars per share)	22.65	25.75	26.00
Shares under option - ending balance (in dollars per share)	$ 38.58	$ 37.18	$ 33.93	$ 30.20
Total Intrinsic Value
Shares under option - beginning balance	$ 115	$ 177	$ 147
Exercised	3	23	45
Shares under option - beginning balance	$ 26	$ 115	$ 177	$ 147
Weighted - Average Contract Term (Years)
Weighted - Average Contract Term (Years)	5 years 9 months 18 days	5 years 10 months 24 days	6 years 2 months 12 days	6 years 3 months 18 days
Options Exercisable
Options exercisable (in shares)	6,898,251	5,963,530	5,498,330
Weighted - Average Option Price (in dollars per share)	$ 35.06	$ 32.02	$ 28.63
Total Intrinsic Value	$ 26
Weighted - Average Contract Term (Years)	4 years 6 months
Options Not Exercisable
Options not exercisable (in shares)	3,091,283
Weighted - Average Option Price (in dollars per share)	$ 46.45
Total Intrinsic Value	$ 0
Weighted - Average Contract Term (Years)	8 years 7 months 6 days