Common Stock and Equity-Based Compensation - AmeriGas Common Unit Based Awards in Common Units and Cash (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
AmeriGas Performance Unit awards
Share-based Compensation Arrangement by Share-based Payment Award
Number of Common Units subject to original awards granted (in shares)	53,800	44,800	55,750
Fiscal year granted	2014	2013	2012
Payment of awards:
AmeriGas Partners Common Units issued, net of units withheld for taxes (in shares)	29,489	23,017	0
Cash paid	$ 2.9	$ 1.7	$ 0.0
AmeriGas Stock Unit awards
Share-based Compensation Arrangement by Share-based Payment Award
Number of Common Units subject to original awards granted (in shares)	32,658	20,336	42,532
Payment of awards:
AmeriGas Partners Common Units issued, net of units withheld for taxes (in shares)	3,932	9,272	21,509
Cash paid	$ 0.1	$ 0.4	$ 0.8