Condensed Financial Information of Registrant (Parent Company) - Balance Sheets (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Current assets
Cash and cash equivalents	$ 558.4	$ 502.8	$ 369.7	$ 419.5
Total current assets	1,697.5	1,423.8
Property, plant and equipment, net	5,537.0	5,238.0
Other assets	259.0	217.7
Total assets	11,582.2	10,847.2	10,514.2
Current liabilities
Total current liabilities	1,690.1	1,442.0
Commitments and contingencies
Common stockholders’ equity:
Common Stock, without par value (authorized – 450,000,000 shares; issued – 173,987,691 and 173,894,141 shares, respectively)	1,188.6	1,201.6
Retained earnings	2,106.7	1,834.1
Accumulated other comprehensive loss	(93.4)	(154.7)
Treasury stock, at cost	(38.6)	(36.9)
Total UGI Corporation stockholders’ equity	3,163.3	2,844.1
Total liabilities and equity	$ 11,582.2	$ 10,847.2
Condensed Financial Information of Registrant [Abstract]
Common stock, shares authorized	450,000,000	450,000,000
Common stock, shares issued	173,987,691	173,894,141
Parent Company
Current assets
Cash and cash equivalents	$ 15.8	$ 4.8	$ 1.9	$ 0.8
Accounts receivable – related parties	4.5	9.2
Prepaid expenses and other current assets	15.6	5.0
Total current assets	35.9	19.0
Property, plant and equipment, net	0.4	0.0
Investments in subsidiaries	3,119.7	2,825.7
Other assets	82.0	69.8
Total assets	3,238.0	2,914.5
Current liabilities
Accounts and notes payable	12.3	11.4
Accrued liabilities	5.9	4.4
Total current liabilities	18.2	15.8
Noncurrent liabilities	56.5	54.6
Commitments and contingencies
Common stockholders’ equity:
Common Stock, without par value (authorized – 450,000,000 shares; issued – 173,987,691 and 173,894,141 shares, respectively)	1,188.6	1,201.6
Retained earnings	2,106.7	1,834.1
Accumulated other comprehensive loss	(93.4)	(154.7)
Treasury stock, at cost	(38.6)	(36.9)
Total UGI Corporation stockholders’ equity	3,163.3	2,844.1
Total liabilities and equity	$ 3,238.0	$ 2,914.5
Condensed Financial Information of Registrant [Abstract]
Common stock, shares authorized	450,000,000	450,000,000
Common stock, shares issued	173,987,691	173,894,141