AmeriGas Merger, Acquisitions and Dispositions - Total Cash Paid and Liabilities Incurred (Details) $ in Millions	12 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($) mi
Business Acquisition [Line Items]
Natural gas lines, acquired (in miles) | mi			21
Payments to acquire long-term investments			$ 20
UGI International
Business Acquisition [Line Items]
Total cash paid	$ 18		49
Liabilities incurred	0		0
Total purchase price	$ 18		49
Midstream & Marketing
Business Acquisition [Line Items]
Total cash paid		$ 16	15
Liabilities incurred		7	0
Total purchase price		$ 23	$ 15