Employee Retirement Plans - Components of Net Periodic Pension Expense and Other Postretirement Benefit Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Pension Benefits
Defined Benefit Plan Disclosure
Service cost	$ 8,469	$ 9,038
Interest cost	25,358	24,394
Other Postretirement Benefits
Defined Benefit Plan Disclosure
Service cost	147	303
Interest cost	448	460
UGI Utilities Employees | Pension Benefits
Defined Benefit Plan Disclosure
Service cost	7,525	8,091	$ 6,927
Interest cost	23,067	22,157	23,270
Expected return on assets	(31,107)	(29,986)	(28,668)
Amortization of:
Prior service cost (benefit)	250	325	348
Actuarial loss	11,936	14,825	9,571
Net benefit cost (benefit)	11,671	15,412	11,448
Change in associated regulatory liabilities	0	0	0
Net benefit cost (benefit) after change in regulatory liabilities	11,671	15,412	11,448
UGI Utilities Employees | Other Postretirement Benefits
Defined Benefit Plan Disclosure
Service cost	267	273	183
Interest cost	447	431	465
Expected return on assets	(709)	(656)	(596)
Amortization of:
Prior service cost (benefit)	(440)	(641)	(641)
Actuarial loss	94	108	98
Net benefit cost (benefit)	(341)	(485)	(491)
Change in associated regulatory liabilities	(490)	(490)	971
Net benefit cost (benefit) after change in regulatory liabilities	$ (831)	$ (975)	$ 480