Acquisitions - Total Cash Paid and Liabilities Incurred (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
AmeriGas Propane
Business Acquisition [Line Items]
Total cash paid	$ 36.8	$ 37.6	$ 20.8
Liabilities incurred	10.8	11.8	4.2
Total purchase price	47.6	49.4	25.0
UGI International
Business Acquisition [Line Items]
Total cash paid	99.7	24.1	17.6
Liabilities incurred	20.6	0.0	0.0
Total purchase price	$ 120.3	$ 24.1	$ 17.6