Segment Information - Schedule of Segment Reporting Information (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2017
Segment Reporting Information
Revenues	$ 2,125.2	$ 1,679.5
Cost of sales	1,137.4	647.4
Segment profit:
Operating (loss) income	391.8	466.2
Income (loss) from equity investees	1.0	(0.2)
(Losses) gains on foreign currency contracts, net	(4.8)	1.3
Loss on extinguishments of debt	0.0	(33.2)
Interest expense	(58.2)	(55.4)
Income (loss) before income taxes	329.8	378.7
Noncontrolling interests’ net (loss) income	68.3	60.2
Depreciation and amortization	110.3	98.1
Capital expenditures (including the effects of accruals)	128.5	173.6
Total assets	12,343.9	11,300.5	$ 11,582.2
Short-term borrowings	586.1	234.4	366.9
Goodwill	3,185.5	2,935.8	$ 3,107.2
Eliminations
Segment Reporting Information
Revenues	(97.1)	(68.5)
Cost of sales	(96.0)	(67.7)
Segment profit:
Operating (loss) income	0.2	0.1
Income (loss) from equity investees	0.0	0.0
(Losses) gains on foreign currency contracts, net	0.0	0.0
Loss on extinguishments of debt		0.0
Interest expense	0.0	0.0
Income (loss) before income taxes	0.2	0.1
Noncontrolling interests’ net (loss) income	0.0	0.0
Depreciation and amortization	0.0	0.0
Capital expenditures (including the effects of accruals)	0.0	0.0
Total assets	(62.6)	(107.9)
Short-term borrowings	0.0	0.0
Goodwill	0.0	0.0
Eliminations | AmeriGas Propane
Segment Reporting Information
Revenues	0.0	0.0
Eliminations | UGI International
Segment Reporting Information
Revenues	0.0	0.0
Eliminations | Midstream & Marketing
Segment Reporting Information
Revenues	78.2	60.2
Eliminations | UGI Utilities
Segment Reporting Information
Revenues	17.7	7.5
Corporate, Intersegment Eliminations & Other
Segment Reporting Information
Revenues	1.2	0.8
Operating Segments | AmeriGas Propane
Segment Reporting Information
Revenues	787.3	677.2
Cost of sales	366.1	260.7
Segment profit:
Operating (loss) income	147.9	141.9
Income (loss) from equity investees	0.0	0.0
(Losses) gains on foreign currency contracts, net	0.0	0.0
Loss on extinguishments of debt	0.0	(33.2)
Interest expense	(40.6)	(40.0)
Income (loss) before income taxes	107.3	68.7
Partnership Adjusted EBITDA	194.1	185.1
Noncontrolling interests’ net (loss) income	68.0	41.2
Depreciation and amortization	47.4	44.6
Capital expenditures (including the effects of accruals)	23.6	26.4
Total assets	4,206.2	4,217.9
Short-term borrowings	263.5	77.5
Goodwill	2,001.3	1,978.5
Operating Segments | UGI International
Segment Reporting Information
Revenues	784.2	539.1
Cost of sales	484.8	258.0
Segment profit:
Operating (loss) income	93.1	88.9
Income (loss) from equity investees	(0.2)	(0.2)
(Losses) gains on foreign currency contracts, net	(4.7)	0.1
Loss on extinguishments of debt		0.0
Interest expense	(5.6)	(4.8)
Income (loss) before income taxes	82.6	84.0
Noncontrolling interests’ net (loss) income	(0.3)	0.2
Depreciation and amortization	32.2	27.9
Capital expenditures (including the effects of accruals)	21.7	21.5
Total assets	3,450.1	2,853.4
Short-term borrowings	41.1	3.5
Goodwill	990.6	763.7
Operating Segments | Midstream & Marketing
Segment Reporting Information
Revenues	249.8	209.6
Cost of sales	239.0	191.8
Segment profit:
Operating (loss) income	52.3	49.7
Income (loss) from equity investees	1.2	0.0
(Losses) gains on foreign currency contracts, net	0.0	0.0
Loss on extinguishments of debt		0.0
Interest expense	(0.9)	(0.6)
Income (loss) before income taxes	52.6	49.1
Noncontrolling interests’ net (loss) income	0.0	0.0
Depreciation and amortization	10.1	8.0
Capital expenditures (including the effects of accruals)	11.3	61.5
Total assets	1,325.1	1,178.4
Short-term borrowings	100.0	55.0
Goodwill	11.5	11.5
Operating Segments | UGI Utilities
Segment Reporting Information
Revenues	305.4	253.9
Cost of sales	151.8	109.5
Segment profit:
Operating (loss) income	96.3	82.2
Income (loss) from equity investees	0.0	0.0
(Losses) gains on foreign currency contracts, net	0.0	0.0
Loss on extinguishments of debt		0.0
Interest expense	(10.9)	(10.0)
Income (loss) before income taxes	85.4	72.2
Noncontrolling interests’ net (loss) income	0.0	0.0
Depreciation and amortization	20.4	17.4
Capital expenditures (including the effects of accruals)	71.7	64.1
Total assets	3,174.7	2,898.5
Short-term borrowings	181.5	98.4
Goodwill	182.1	182.1
Corporate & Other
Segment Reporting Information
Revenues	(1.5)	(0.3)
Cost of sales	(8.3)	(104.9)
Segment profit:
Operating (loss) income	2.0	103.4
Income (loss) from equity investees	0.0	0.0
(Losses) gains on foreign currency contracts, net	(0.1)	1.2
Loss on extinguishments of debt		0.0
Interest expense	(0.2)	0.0
Income (loss) before income taxes	1.7	104.6
Noncontrolling interests’ net (loss) income	0.6	18.8
Depreciation and amortization	0.2	0.2
Capital expenditures (including the effects of accruals)	0.2	0.1
Total assets	250.4	260.2
Short-term borrowings	0.0	0.0
Goodwill	0.0	0.0
Gains (losses) on unsettled commodity derivative instruments, net	$ 6.6	$ 105.5