Common Stock and Equity-Based Compensation - Schedule of Payment for UGI Performance Unit and UGI Stock Unit Awards in Shares and Cash (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
UGI Performance Units
Share-based Compensation Arrangement by Share-based Payment Award
Number of original awards granted (in shares)	178,450	308,362	294,300
Fiscal year granted	2014	2013	2012
Payment of awards:
Shares of UGI Common Stock issued, net of shares withheld for taxes	138,985	209,592	188,418
Cash paid	$ 10.9	$ 13.9	$ 13.3
UGI Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Number of original awards granted (in shares)	43,699	51,037	67,419
Payment of awards:
Shares of UGI Common Stock issued, net of shares withheld for taxes	15,990	39,422	44,034
Cash paid	$ 0.3	$ 0.7	$ 0.8