Employee Retirement Plans - Fair Value of U.S. Pension Plan and VEBA Trust Assets (Details) - Pension Benefits - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 736	$ 585	$ 547
U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	717	566
U.S. | U.S. equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	35	27
U.S. | UGI Corporation Common Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	35	27
U.S. | Total common collective trust funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	655	539
U.S. | U.S. equity index investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	124	123
U.S. | Non-U.S. equity index investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	155	141
U.S. | Global equity index investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	115	70
U.S. | Bond index mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	254	200
U.S. | Cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7	5
U.S. | Alternative investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 27	$ 0