Income Tax Reform - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended				9 Months Ended		12 Months Ended
	Mar. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Operating Loss Carryforwards [Line Items]
Reduction in net deferred income tax liabilities due to the remeasuring of existing federal deferred income tax assets and liabilities		$ 0.8				$ 389.6
Regulatory liability, excess deferred federal income taxes due to tax reform				$ 216.1
Increase in regulatory liabilities for the tax effect of future revenue reductions				87.8
Estimated deferred tax benefit resulting from future income tax reduction		6.1				60.6
Foreign Tax Authority | French Parliament
Operating Loss Carryforwards [Line Items]
Effective income tax rate reconciliation, change in enacted tax rate, amount (excluding tax cuts and jobs act of 2017 Impact)		(0.2)					$ 4.7
Foreign Tax Authority | French Parliament | January 1, 2022 (Fiscal 2023)
Operating Loss Carryforwards [Line Items]
Income tax benefit, continuing operations, adjustment of deferred taxes		0.1	$ 3.7	$ 17.3		$ 13.5
Increase in per share, basic and diluted resulting from future income tax reduction (in dollars per share)						$ 0.08
Foreign Tax Authority | French Parliament | January 1, 2020 (Fiscal 2021)
Operating Loss Carryforwards [Line Items]
Income tax benefit, continuing operations, adjustment of deferred taxes					$ 27.4
Increase in per share, basic and diluted resulting from future income tax reduction (in dollars per share)					$ 0.15
Scenario, Forecast
Operating Loss Carryforwards [Line Items]
Effective income tax rate reconciliation, blended federal rate								24.50%
UGI Utilities
Operating Loss Carryforwards [Line Items]
PUC temporary rates order, reduction in revenue	$ 1.4	22.7				$ 24.1
Regulatory assets		$ 360.1				360.1	$ 398.8		$ 368.9
Income Tax Benefits | UGI Utilities
Operating Loss Carryforwards [Line Items]
PUC temporary rates order, reduction in revenue						17.1
Future Amortization Of Regulatory Liabilities | UGI Utilities
Operating Loss Carryforwards [Line Items]
PUC temporary rates order, reduction in revenue						$ 7.0