Employee Retirement Plans - Fair Value of U.S. Pension Plan and VEBA Trust Assets (Details) - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Pension Benefits
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 546.8	$ 563.3	$ 529.2
Pension Benefits | U.S.
Defined Benefit Plan Disclosure
Fair value of plan assets	529.1	531.7
Pension Benefits | U.S. | S&P 500 Index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	176.4	188.4
Pension Benefits | U.S. | Small and midcap equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	72.8	75.7
Pension Benefits | U.S. | UGI Corporation Common Stock
Defined Benefit Plan Disclosure
Fair value of plan assets	40.9	45.2
Pension Benefits | U.S. | Total domestic equity investments
Defined Benefit Plan Disclosure
Fair value of plan assets	290.1	309.3
Pension Benefits | U.S. | International index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	62.1	62.9
Pension Benefits | U.S. | Bond index mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	170.5	154.3
Pension Benefits | U.S. | Cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	6.4	5.2
Pension Benefits | U.S. | Fixed income funds & cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	176.9	159.5
Pension Benefits | U.S. | Level 1
Defined Benefit Plan Disclosure
Fair value of plan assets	522.7	526.5
Pension Benefits | U.S. | Level 1 | S&P 500 Index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	176.4	188.4
Pension Benefits | U.S. | Level 1 | Small and midcap equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	72.8	75.7
Pension Benefits | U.S. | Level 1 | UGI Corporation Common Stock
Defined Benefit Plan Disclosure
Fair value of plan assets	40.9	45.2
Pension Benefits | U.S. | Level 1 | Total domestic equity investments
Defined Benefit Plan Disclosure
Fair value of plan assets	290.1	309.3
Pension Benefits | U.S. | Level 1 | International index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	62.1	62.9
Pension Benefits | U.S. | Level 1 | Bond index mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	170.5	154.3
Pension Benefits | U.S. | Level 1 | Cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Pension Benefits | U.S. | Level 1 | Fixed income funds & cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	170.5	154.3
Pension Benefits | U.S. | Level 2 | S&P 500 Index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Pension Benefits | U.S. | Level 2 | Small and midcap equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Pension Benefits | U.S. | Level 2 | UGI Corporation Common Stock
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Pension Benefits | U.S. | Level 2 | Total domestic equity investments
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Pension Benefits | U.S. | Level 2 | International index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Pension Benefits | U.S. | Level 2 | Bond index mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Pension Benefits | U.S. | Level 3
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Pension Benefits | U.S. | Level 3 | S&P 500 Index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Pension Benefits | U.S. | Level 3 | Small and midcap equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Pension Benefits | U.S. | Level 3 | UGI Corporation Common Stock
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Pension Benefits | U.S. | Level 3 | Total domestic equity investments
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Pension Benefits | U.S. | Level 3 | International index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Pension Benefits | U.S. | Level 3 | Bond index mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Pension Benefits | U.S. | Level 3 | Cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Pension Benefits | U.S. | Level 3 | Fixed income funds & cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Pension Benefits | U.S. | Other
Defined Benefit Plan Disclosure
Fair value of plan assets	6.4	5.2
Pension Benefits | U.S. | Other | S&P 500 Index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Pension Benefits | U.S. | Other | Small and midcap equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Pension Benefits | U.S. | Other | UGI Corporation Common Stock
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Pension Benefits | U.S. | Other | Total domestic equity investments
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Pension Benefits | U.S. | Other | International index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Pension Benefits | U.S. | Other | Bond index mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
Pension Benefits | U.S. | Other | Cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	6.4	5.2
Pension Benefits | U.S. | Other | Fixed income funds & cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	6.4	5.2
VEBA
Defined Benefit Plan Disclosure
Fair value of plan assets	16.2	15.3
VEBA | S&P 500 Index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	10.5	10.1
VEBA | Bond index mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	5.5	4.9
VEBA | Cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	0.2	0.3
VEBA | Level 1
Defined Benefit Plan Disclosure
Fair value of plan assets	16.0	15.0
VEBA | Level 1 | S&P 500 Index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	10.5	10.1
VEBA | Level 1 | Bond index mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	5.5	4.9
VEBA | Level 1 | Cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
VEBA | Level 2 | S&P 500 Index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
VEBA | Level 2 | Bond index mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
VEBA | Level 3
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
VEBA | Level 3 | S&P 500 Index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
VEBA | Level 3 | Bond index mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
VEBA | Level 3 | Cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
VEBA | Other
Defined Benefit Plan Disclosure
Fair value of plan assets	0.2	0.3
VEBA | Other | S&P 500 Index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
VEBA | Other | Bond index mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0.0	0.0
VEBA | Other | Cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 0.2	$ 0.3