AmeriGas Merger, Acquisitions and Dispositions - Total Cash Paid and Liabilities Incurred (Details) $ in Millions	12 Months Ended
	Sep. 30, 2020 USD ($) mi	Sep. 30, 2019 USD ($) mi MW	Sep. 30, 2018 USD ($)
Business Acquisition [Line Items]
Natural gas lines, acquired (in miles) | mi	21	60
Payments to acquire long-term investments	$ 20	$ 70
Natural gas-fired peaking turbine, acquired (mw) | MW		44
UGI International
Business Acquisition [Line Items]
Total cash paid		$ 49	$ 122
Liabilities incurred		0	0
Total purchase price		49	122
Midstream & Marketing
Business Acquisition [Line Items]
Total cash paid	16	15
Liabilities incurred	7	0
Total purchase price	$ 23	$ 15
AmeriGas Propane
Business Acquisition [Line Items]
Total cash paid			10
Liabilities incurred			3
Total purchase price			$ 13