Employee Retirement Plans - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plan Disclosure
Estimated amortization of net actuarial losses for Fiscal 2017	$ 7,000
Amortization of net prior service costs (credits)	(200)
Projected benefit obligations of unfunded and non qualified supplemental executive retirement plans	3,803	$ 4,222
Net cost to sponsor unfunded and non-qualified supplemental executive retirement plans	$ 355	$ 605	$ 353
The aggregate holdings of all qualifying employer securities not to exceed the fair value of trust assets at the time of purchase	10.00%
Percentage of UGI Common Stock represented Pension Plan Assets	8.50%	7.70%
Cost of benefits under Utilities Savings Plan	$ 3,391	$ 2,829	2,409
Pension Benefits
Defined Benefit Plan Disclosure
ABO for the Pension Plans	572,801	605,237
Benefit obligations	611,191	639,245	645,444
Employer contributions	15,079	11,395	9,869
Pension Benefits | Employees of UGI and Certain of its Other Subsidiaries
Defined Benefit Plan Disclosure
Benefit obligations	60,904	62,458
Other Postretirement Benefits
Defined Benefit Plan Disclosure
Benefit obligations	10,684	11,904	$ 12,075
Employer contributions	0	85
Other Postretirement Benefits | Employees of UGI and Certain of its Other Subsidiaries
Defined Benefit Plan Disclosure
ABO for the Pension Plans	$ 880	$ 996