Employee Retirement Plans - Fair Value of U.S. Pension Plan and VEBA Trust Assets (Details) - USD ($) $ in Millions	Sep. 30, 2015	Sep. 30, 2014
U.S Pension Plans
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 430.8	$ 442.4
U.S Pension Plans | Domestic equity investments:
Defined Benefit Plan Disclosure
Fair value of plan assets	242.0	245.8
U.S Pension Plans | S&P 500 Index Equity Mutual Funds
Defined Benefit Plan Disclosure
Fair value of plan assets	147.3	152.6
U.S Pension Plans | Small and Midcap Equity Mutual Funds
Defined Benefit Plan Disclosure
Fair value of plan assets	40.6	41.4
U.S Pension Plans | Smallcap Common Stocks
Defined Benefit Plan Disclosure
Fair value of plan assets	10.7	9.3
U.S Pension Plans | UGI Corporation Common Stock
Defined Benefit Plan Disclosure
Fair value of plan assets	43.4	42.5
U.S Pension Plans | International Index Equity Mutual Funds
Defined Benefit Plan Disclosure
Fair value of plan assets	43.9	49.9
U.S Pension Plans | Fixed income investments:
Defined Benefit Plan Disclosure
Fair value of plan assets	144.9	146.7
U.S Pension Plans | Bond Index Mutual Funds
Defined Benefit Plan Disclosure
Fair value of plan assets	140.8	141.0
U.S Pension Plans | Cash Equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	4.1	5.7
VEBA Trust
Defined Benefit Plan Disclosure
Fair value of plan assets	12.5	12.8
VEBA Trust | S&P 500 Index Equity Mutual Funds
Defined Benefit Plan Disclosure
Fair value of plan assets	8.4	8.7
VEBA Trust | Bond Index Mutual Funds
Defined Benefit Plan Disclosure
Fair value of plan assets	3.8	3.7
VEBA Trust | Cash Equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	0.3	0.4
Level 1 | U.S Pension Plans
Defined Benefit Plan Disclosure
Fair value of plan assets	426.7	436.7
Level 1 | U.S Pension Plans | Domestic equity investments:
Defined Benefit Plan Disclosure
Fair value of plan assets	242.0	245.8
Level 1 | U.S Pension Plans | S&P 500 Index Equity Mutual Funds
Defined Benefit Plan Disclosure
Fair value of plan assets	147.3	152.6
Level 1 | U.S Pension Plans | Small and Midcap Equity Mutual Funds
Defined Benefit Plan Disclosure
Fair value of plan assets	40.6	41.4
Level 1 | U.S Pension Plans | Smallcap Common Stocks
Defined Benefit Plan Disclosure
Fair value of plan assets	10.7	9.3
Level 1 | U.S Pension Plans | UGI Corporation Common Stock
Defined Benefit Plan Disclosure
Fair value of plan assets	43.4	42.5
Level 1 | U.S Pension Plans | International Index Equity Mutual Funds
Defined Benefit Plan Disclosure
Fair value of plan assets	43.9	49.9
Level 1 | U.S Pension Plans | Fixed income investments:
Defined Benefit Plan Disclosure
Fair value of plan assets	140.8	141.0
Level 1 | U.S Pension Plans | Bond Index Mutual Funds
Defined Benefit Plan Disclosure
Fair value of plan assets	140.8	141.0
Level 1 | VEBA Trust
Defined Benefit Plan Disclosure
Fair value of plan assets	12.2	12.4
Level 1 | VEBA Trust | S&P 500 Index Equity Mutual Funds
Defined Benefit Plan Disclosure
Fair value of plan assets	8.4	8.7
Level 1 | VEBA Trust | Bond Index Mutual Funds
Defined Benefit Plan Disclosure
Fair value of plan assets	3.8	3.7
Level 2 | U.S Pension Plans
Defined Benefit Plan Disclosure
Fair value of plan assets	4.1	5.7
Level 2 | U.S Pension Plans | Fixed income investments:
Defined Benefit Plan Disclosure
Fair value of plan assets	4.1	5.7
Level 2 | U.S Pension Plans | Cash Equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	4.1	5.7
Level 2 | VEBA Trust
Defined Benefit Plan Disclosure
Fair value of plan assets	0.3	0.4
Level 2 | VEBA Trust | Cash Equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 0.3	$ 0.4