Common Stock and Equity-Based Compensation - Weighted Average Assumption Used to Determine the Fair Value of AmeriGas Performance Unit Awards and Related Compensation Costs (Details) - AmeriGas Performance Units	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award
Risk-free rate	1.50%	1.30%	0.90%
Expected life	3 years	3 years	3 years
Expected volatility (as a percent)	21.70%	20.60%	19.20%
Dividend yield (as a percent)	7.80%	10.70%	6.80%