Employee Retirement Plans - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Defined Benefit Plan Disclosure
Estimated amortization of net actuarial losses for Fiscal 2017	$ 12,000
Amortization of net prior service costs (credits)	$ (250)
Percentage point change in assumed health care cost trend rates	1.00%
Projected benefit obligations of unfunded and non qualified supplemental executive retirement plans	$ 4,222	$ 3,628
Net cost to sponsor unfunded and non-qualified supplemental executive retirement plans	$ 605	$ 353	$ 445
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	7.70%	8.00%
Cost of benefits under Utilities Savings Plan	$ 2,829	$ 2,409	2,162
Pension Benefits
Defined Benefit Plan Disclosure
ABO for the Pension Plans	605,237	601,255
Benefit obligations	639,245	645,444	563,621
Employer contributions	11,395	9,869	11,131
Pension Benefits | Employees of UGI and Certain of its Other Subsidiaries
Defined Benefit Plan Disclosure
Benefit obligations	62,458	63,847
Other Postretirement Benefits
Defined Benefit Plan Disclosure
Benefit obligations	11,904	12,075	$ 10,676
Employer contributions	85	98
Other Postretirement Benefits | Employees of UGI and Certain of its Other Subsidiaries
Defined Benefit Plan Disclosure
ABO for the Pension Plans	$ 996	$ 951