Commitments and Contingencies - Contingencies (Details) $ in Millions			12 Months Ended
	Oct. 01, 2020 agreement	Sep. 30, 2020 USD ($) agreement	Dec. 31, 2017 record_of_decision	Dec. 31, 2008 lb	Dec. 31, 2007 lb	Sep. 30, 2021 USD ($) subsidiary	Sep. 30, 2017 USD ($)
Loss Contingencies [Line Items]
Environmental expenditures cap during year						$ 5
Amount of propane in cylinders being sold | lb					17
Reduced amount of propane in cylinders being sold | lb				15
CPG, PNG and UGI Gas COAs
Loss Contingencies [Line Items]
Accrued liabilities for environmental investigation and remediation costs related to CPG-COA and PNG-COA		$ 53				$ 50
UGI Utilities, Inc.
Loss Contingencies [Line Items]
Number of COAs | agreement	1	3
UGI Utilities, Inc. | CPG and PNG
Loss Contingencies [Line Items]
Number of subsidiaries acquired with similar histories | subsidiary						2
AmeriGas OLP | Saranac Lake, New York | New York State Department of Environment Conservation Remediation Plan
Loss Contingencies [Line Items]
Accrued liabilities for environmental investigation and remediation costs related to CPG-COA and PNG-COA		$ 8				$ 8
Number of records of decisions drafted | record_of_decision			3
Estimated remediation plan cost							$ 28