Employee Retirement Plans - Fair Value of Pension Plan and VEBA Trust Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Pension Benefits
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	$ 463,432	$ 430,789	$ 442,465
Pension Benefits | Domestic Equity Investments
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	250,503	242,037
Pension Benefits | S&P 500 Index Equity Mutual Funds
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	158,906	147,266
Pension Benefits | Small and Midcap Equity Mutual Funds
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	43,170	40,625
Pension Benefits | Smallcap Common Stocks
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	11,414	10,727
Pension Benefits | UGI Corporation Common Stock
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	37,013	43,419
Pension Benefits | International Index Equity Mutual Funds
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	47,324	43,906
Pension Benefits | Fixed Income Investments
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	165,605	144,846
Pension Benefits | Bond Index Mutual Fund
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	147,794	140,776
Pension Benefits | Cash Equivalents
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	17,811	4,070
Pension Benefits | Level 1
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	445,621	426,719
Pension Benefits | Level 1 | Domestic Equity Investments
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	250,503	242,037
Pension Benefits | Level 1 | S&P 500 Index Equity Mutual Funds
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	158,906	147,266
Pension Benefits | Level 1 | Small and Midcap Equity Mutual Funds
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	43,170	40,625
Pension Benefits | Level 1 | Smallcap Common Stocks
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	11,414	10,727
Pension Benefits | Level 1 | UGI Corporation Common Stock
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	37,013	43,419
Pension Benefits | Level 1 | International Index Equity Mutual Funds
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	47,324	43,906
Pension Benefits | Level 1 | Fixed Income Investments
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	147,794	140,776
Pension Benefits | Level 1 | Bond Index Mutual Fund
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	147,794	140,776
Pension Benefits | Level 1 | Cash Equivalents
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
Pension Benefits | Level 2
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	17,811	4,070
Pension Benefits | Level 2 | Domestic Equity Investments
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
Pension Benefits | Level 2 | S&P 500 Index Equity Mutual Funds
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
Pension Benefits | Level 2 | Small and Midcap Equity Mutual Funds
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
Pension Benefits | Level 2 | Smallcap Common Stocks
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
Pension Benefits | Level 2 | UGI Corporation Common Stock
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
Pension Benefits | Level 2 | International Index Equity Mutual Funds
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
Pension Benefits | Level 2 | Fixed Income Investments
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	17,811	4,070
Pension Benefits | Level 2 | Bond Index Mutual Fund
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
Pension Benefits | Level 2 | Cash Equivalents
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	17,811	4,070
Pension Benefits | Level 3
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
Pension Benefits | Level 3 | Domestic Equity Investments
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
Pension Benefits | Level 3 | S&P 500 Index Equity Mutual Funds
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
Pension Benefits | Level 3 | Small and Midcap Equity Mutual Funds
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
Pension Benefits | Level 3 | Smallcap Common Stocks
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
Pension Benefits | Level 3 | UGI Corporation Common Stock
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
Pension Benefits | Level 3 | International Index Equity Mutual Funds
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
Pension Benefits | Level 3 | Fixed Income Investments
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
Pension Benefits | Level 3 | Bond Index Mutual Fund
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
Pension Benefits | Level 3 | Cash Equivalents
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
VEBA Trust
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	13,715	12,523
VEBA Trust | S&P 500 Index Equity Mutual Funds
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	9,583	8,434
VEBA Trust | Bond Index Mutual Fund
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	4,019	3,832
VEBA Trust | Cash Equivalents
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	113	257
VEBA Trust | Level 1
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	13,602	12,266
VEBA Trust | Level 1 | S&P 500 Index Equity Mutual Funds
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	9,583	8,434
VEBA Trust | Level 1 | Bond Index Mutual Fund
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	4,019	3,832
VEBA Trust | Level 1 | Cash Equivalents
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
VEBA Trust | Level 2
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	113	257
VEBA Trust | Level 2 | S&P 500 Index Equity Mutual Funds
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
VEBA Trust | Level 2 | Bond Index Mutual Fund
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
VEBA Trust | Level 2 | Cash Equivalents
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	113	257
VEBA Trust | Level 3
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
VEBA Trust | Level 3 | S&P 500 Index Equity Mutual Funds
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
VEBA Trust | Level 3 | Bond Index Mutual Fund
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	0	0
VEBA Trust | Level 3 | Cash Equivalents
Fair Value of Pension Plan Assets
Fair Value of Plan Assets	$ 0	$ 0