Summary of Significant Accounting Policies - Schedule of Income Per Limited Partner Unit (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Net income attributable to AmeriGas Partners, L.P.	$ 104,421	$ 91,954
Adjust for general partner share and theoretical distributions of net income attributable to AmeriGas Partners, L.P. to the general partner in accordance with the two-class method for MLPs	(14,202)	(11,352)
Common Unitholders’ interest in net income attributable to AmeriGas Partners, L.P. under the two-class method for MLPs	$ 90,219	$ 80,602
Weighted average Common Units outstanding—basic (in shares)	93,016	92,967
Potentially dilutive Common Units (in units)	64	52
Weighted average Common Units outstanding—diluted (in shares)	93,080	93,019