Commitments and Contingencies - Contingencies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 record_of_decision	Dec. 31, 2008 lb	Dec. 31, 2007 lb	Sep. 30, 2020 USD ($) subsidiary	Sep. 30, 2019 USD ($)	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 | 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
Number of records of decisions drafted | record_of_decision	3
Estimated remediation plan cost						$ 28