Employee Retirement Plans - Fair Value of U.S. Pension Plan and VEBA Trust Assets (Details) - Pension Benefits - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 585	$ 547	$ 563
U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	566	529
U.S. | UGI Corporation Common Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	27	41
U.S. | Total domestic equity investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	27	290
U.S. | U.S. equity index investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	123
U.S. | U.S. equity index investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	539
U.S. | International index equity mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		62
U.S. | Global equity index investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	70
U.S. | Bond index mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	200	171
U.S. | S&P 500 Index equity mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		176
U.S. | Small and midcap equity mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		73
U.S. | Cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	6
U.S. | Fixed income funds & cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		177
U.S. | Defined Benefit Plan Non Us Equity Index Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	141
U.S. | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	27	523
U.S. | Level 1 | UGI Corporation Common Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	27	41
U.S. | Level 1 | Total domestic equity investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	27	290
U.S. | Level 1 | International index equity mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		62
U.S. | Level 1 | Bond index mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		171
U.S. | Level 1 | S&P 500 Index equity mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		176
U.S. | Level 1 | Small and midcap equity mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		73
U.S. | Level 1 | Fixed income funds & cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		171
U.S. | Level 2 | UGI Corporation Common Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. | Level 2 | Total domestic equity investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. | Level 2 | International index equity mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
U.S. | Level 2 | Bond index mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
U.S. | Level 2 | S&P 500 Index equity mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
U.S. | Level 2 | Small and midcap equity mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
U.S. | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. | Level 3 | UGI Corporation Common Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. | Level 3 | Total domestic equity investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. | Level 3 | International index equity mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
U.S. | Level 3 | Bond index mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
U.S. | Level 3 | S&P 500 Index equity mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
U.S. | Level 3 | Small and midcap equity mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
U.S. | Level 3 | Fixed income funds & cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
U.S. | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	539	6
U.S. | Other | U.S. equity index investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	123
U.S. | Other | U.S. equity index investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	539
U.S. | Other | Global equity index investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	70
U.S. | Other | Bond index mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	200
U.S. | Other | Cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	6
U.S. | Other | Fixed income funds & cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 6
U.S. | Other | Defined Benefit Plan Non Us Equity Index Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 141