Employee Retirement Plans - Fair Value of Pension Plan and VEBA Trust Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
VEBA Trust
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 15,348	$ 14,771
Other	301	409
VEBA Trust | S&P 500 Index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	10,074	9,318
Other	0	0
VEBA Trust | Bond index mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	4,973	5,044
Other	0	0
VEBA Trust | Cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	301	409
Other	301	409
VEBA Trust | Level 1
Defined Benefit Plan Disclosure
Fair value of plan assets	15,047	14,362
VEBA Trust | Level 1 | S&P 500 Index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	10,074	9,318
VEBA Trust | Level 1 | Bond index mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	4,973	5,044
VEBA Trust | Level 1 | Cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
VEBA Trust | Level 2
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
VEBA Trust | Level 2 | S&P 500 Index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
VEBA Trust | Level 2 | Bond index mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
VEBA Trust | Level 2 | Cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
VEBA Trust | Level 3
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
VEBA Trust | Level 3 | S&P 500 Index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
VEBA Trust | Level 3 | Bond index mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
VEBA Trust | Level 3 | Cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Pension Benefits
Defined Benefit Plan Disclosure
Fair value of plan assets	531,736	498,080	$ 463,432
Pension Benefits | U.S. Pension Plan
Defined Benefit Plan Disclosure
Fair value of plan assets	531,714	498,077
Other	5,198	5,332
Pension Benefits | U.S. Pension Plan | Total domestic equity investments
Defined Benefit Plan Disclosure
Fair value of plan assets	309,264	274,904
Other	0	0
Pension Benefits | U.S. Pension Plan | S&P 500 Index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	188,437	171,600
Other	0	0
Pension Benefits | U.S. Pension Plan | Small and midcap equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	75,675	65,167
Other	0	0
Pension Benefits | U.S. Pension Plan | UGI Corporation Common Stock
Defined Benefit Plan Disclosure
Fair value of plan assets	45,152	38,137
Other	0	0
Pension Benefits | U.S. Pension Plan | International index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	62,907	61,613
Other	0	0
Pension Benefits | U.S. Pension Plan | Total fixed income investments
Defined Benefit Plan Disclosure
Fair value of plan assets	159,543	161,560
Other	5,198	5,332
Pension Benefits | U.S. Pension Plan | Bond index mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	154,345	156,228
Other	0	0
Pension Benefits | U.S. Pension Plan | Cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	5,198	5,332
Other	5,198	5,332
Pension Benefits | U.S. Pension Plan | Level 1
Defined Benefit Plan Disclosure
Fair value of plan assets	526,516	492,745
Pension Benefits | U.S. Pension Plan | Level 1 | Total domestic equity investments
Defined Benefit Plan Disclosure
Fair value of plan assets	309,264	274,904
Pension Benefits | U.S. Pension Plan | Level 1 | S&P 500 Index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	188,437	171,600
Pension Benefits | U.S. Pension Plan | Level 1 | Small and midcap equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	75,675	65,167
Pension Benefits | U.S. Pension Plan | Level 1 | UGI Corporation Common Stock
Defined Benefit Plan Disclosure
Fair value of plan assets	45,152	38,137
Pension Benefits | U.S. Pension Plan | Level 1 | International index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	62,907	61,613
Pension Benefits | U.S. Pension Plan | Level 1 | Total fixed income investments
Defined Benefit Plan Disclosure
Fair value of plan assets	154,345	156,228
Pension Benefits | U.S. Pension Plan | Level 1 | Bond index mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	154,345	156,228
Pension Benefits | U.S. Pension Plan | Level 1 | Cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Pension Benefits | U.S. Pension Plan | Level 2
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Pension Benefits | U.S. Pension Plan | Level 2 | Total domestic equity investments
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Pension Benefits | U.S. Pension Plan | Level 2 | S&P 500 Index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Pension Benefits | U.S. Pension Plan | Level 2 | Small and midcap equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Pension Benefits | U.S. Pension Plan | Level 2 | UGI Corporation Common Stock
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Pension Benefits | U.S. Pension Plan | Level 2 | International index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Pension Benefits | U.S. Pension Plan | Level 2 | Total fixed income investments
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Pension Benefits | U.S. Pension Plan | Level 2 | Bond index mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Pension Benefits | U.S. Pension Plan | Level 2 | Cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Pension Benefits | U.S. Pension Plan | Level 3
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Pension Benefits | U.S. Pension Plan | Level 3 | Total domestic equity investments
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Pension Benefits | U.S. Pension Plan | Level 3 | S&P 500 Index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Pension Benefits | U.S. Pension Plan | Level 3 | Small and midcap equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Pension Benefits | U.S. Pension Plan | Level 3 | UGI Corporation Common Stock
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Pension Benefits | U.S. Pension Plan | Level 3 | International index equity mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Pension Benefits | U.S. Pension Plan | Level 3 | Total fixed income investments
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Pension Benefits | U.S. Pension Plan | Level 3 | Bond index mutual funds
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Pension Benefits | U.S. Pension Plan | Level 3 | Cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 0	$ 0