Segment Information - Schedule of Segment Reporting Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2019
Segment Reporting Information [Line Items]
Revenues	$ 1,199.3	$ 1,363.7	$ 5,434.8	$ 6,170.0
Cost of sales	416.6	781.4	2,672.8	3,633.3
Operating income	173.9	9.6	913.0	716.1
Income (loss) from equity investees	7.5	1.5	22.0	4.6
Loss on extinguishments of debt	0.0	0.0	0.0	(6.1)
Other non-operating (expense) income, net	(3.9)	0.7	(3.7)	17.6
Earnings (loss) before interest expense and income taxes	177.5	11.8	931.3	732.2
Interest expense	(80.8)	(60.5)	(247.3)	(181.7)
Income (loss) before income taxes	96.7	(48.7)	684.0	550.5
Noncontrolling interests’ net income (loss)	(0.6)	(44.6)	(0.5)	131.0
Depreciation and amortization	122.5	109.9	362.1	330.0
Capital expenditures (including the effects of accruals)	133.6	166.0	444.4	479.0
Total assets	13,843.4	12,018.9	13,843.4	12,018.9	$ 13,346.6
Short-term borrowings	423.1	380.2	423.1	380.2	796.3
Goodwill	3,482.7	3,159.1	3,482.7	3,159.1	$ 3,456.4
Eliminations
Segment Reporting Information [Line Items]
Revenues	(29.0)	(39.6)	(203.2)	(276.0)
Cost of sales	(28.2)	(38.5)	(200.7)	(272.9)
Operating income	0.1	0.2	0.1	0.2
Income (loss) from equity investees	0.0	0.0	0.0	0.0
Loss on extinguishments of debt				0.0
Other non-operating (expense) income, net	0.0	0.0	0.0	0.0
Earnings (loss) before interest expense and income taxes	0.1	0.2	0.1	0.2
Interest expense	0.0	0.0	0.0	0.0
Income (loss) before income taxes	0.1	0.2	0.1	0.2
Noncontrolling interests’ net income (loss)	0.0	0.0	0.0	0.0
Depreciation and amortization	(0.1)	(0.2)	(0.3)	(0.3)
Capital expenditures (including the effects of accruals)	0.0	0.0	0.0	0.0
Total assets	(364.7)	(116.9)	(364.7)	(116.9)
Short-term borrowings	0.0	0.0	0.0	0.0
Goodwill	0.0	0.0	0.0	0.0
Eliminations | AmeriGas Propane
Segment Reporting Information [Line Items]
Revenues	0.0	0.0	0.0	0.0
Eliminations | UGI International
Segment Reporting Information [Line Items]
Revenues	0.0	0.0	0.0	0.0
Eliminations | Midstream & Marketing
Segment Reporting Information [Line Items]
Revenues	20.8	28.0	162.4	213.7
Eliminations | UGI Utilities
Segment Reporting Information [Line Items]
Revenues	7.5	10.9	38.7	59.8
Intersegment revenues Corporate & Other
Segment Reporting Information [Line Items]
Revenues	0.7	0.7	2.1	2.5
Operating Segments | AmeriGas Propane
Segment Reporting Information [Line Items]
Revenues	450.9	478.7	1,983.3	2,270.5
Cost of sales	177.9	210.3	792.7	1,024.0
Operating income	18.8	(1.2)	390.1	412.7
Income (loss) from equity investees	0.0	0.0	0.0	0.0
Loss on extinguishments of debt				0.0
Other non-operating (expense) income, net	0.0	0.0	0.0	0.0
Earnings (loss) before interest expense and income taxes	18.8	(1.2)	390.1	412.7
Interest expense	(40.2)	(41.6)	(123.9)	(126.2)
Income (loss) before income taxes	(21.4)	(42.8)	266.2	286.5
Noncontrolling interests’ net income (loss)	0.0	(40.7)	0.0	180.1
Depreciation and amortization	45.0	44.0	133.8	134.0
Capital expenditures (including the effects of accruals)	30.0	21.0	104.4	77.8
Total assets	4,311.0	3,789.4	4,311.0	3,789.4
Short-term borrowings	162.0	248.5	162.0	248.5
Goodwill	2,003.0	2,003.0	2,003.0	2,003.0
Operating Segments | UGI International
Segment Reporting Information [Line Items]
Revenues	371.5	486.6	1,726.3	1,980.5
Cost of sales	198.6	278.5	968.6	1,171.8
Operating income	17.5	27.5	230.1	212.7
Income (loss) from equity investees	(0.1)	0.0	0.0	0.1
Loss on extinguishments of debt				0.0
Other non-operating (expense) income, net	2.9	1.2	16.6	5.0
Earnings (loss) before interest expense and income taxes	20.3	28.7	246.7	217.8
Interest expense	(7.9)	(5.8)	(23.2)	(17.3)
Income (loss) before income taxes	12.4	22.9	223.5	200.5
Noncontrolling interests’ net income (loss)	(0.6)	(0.1)	(0.5)	0.2
Depreciation and amortization	30.8	30.8	92.4	92.8
Capital expenditures (including the effects of accruals)	20.0	24.1	61.9	74.0
Total assets	3,208.1	3,168.0	3,208.1	3,168.0
Short-term borrowings	181.1	0.7	181.1	0.7
Goodwill	955.4	956.2	955.4	956.2
Operating Segments | Midstream & Marketing
Segment Reporting Information [Line Items]
Revenues	222.5	267.3	1,017.2	1,269.1
Revenues, before intersegment effect	201.7	239.3	854.8	1,055.4
Cost of sales	159.2	225.4	721.7	1,052.2
Operating income	12.8	2.7	139.2	95.1
Income (loss) from equity investees	7.6	1.5	22.0	4.5
Loss on extinguishments of debt				0.0
Other non-operating (expense) income, net	0.0	0.1	0.0	0.1
Earnings (loss) before interest expense and income taxes	20.4	4.3	161.2	99.7
Interest expense	(11.5)	(0.7)	(34.4)	(1.7)
Income (loss) before income taxes	8.9	3.6	126.8	98.0
Noncontrolling interests’ net income (loss)	0.0	0.0	0.0	0.0
Depreciation and amortization	19.4	11.8	56.8	34.8
Capital expenditures (including the effects of accruals)	15.2	36.4	61.2	93.8
Total assets	2,740.2	1,444.7	2,740.2	1,444.7
Short-term borrowings	40.0	55.0	40.0	55.0
Goodwill	342.2	17.8	342.2	17.8
Operating Segments | UGI Utilities
Segment Reporting Information [Line Items]
Revenues	179.1	163.9	901.0	916.2
Revenues, before intersegment effect	171.6	153.0	862.3	856.4
Cost of sales	67.9	61.0	403.5	438.5
Operating income	20.9	20.4	228.7	217.3
Income (loss) from equity investees	0.0	0.0	0.0	0.0
Loss on extinguishments of debt				0.0
Other non-operating (expense) income, net	0.0	0.4	(0.2)	1.2
Earnings (loss) before interest expense and income taxes	20.9	20.8	228.5	218.5
Interest expense	(13.8)	(12.4)	(40.9)	(36.3)
Income (loss) before income taxes	7.1	8.4	187.6	182.2
Noncontrolling interests’ net income (loss)	0.0	0.0	0.0	0.0
Depreciation and amortization	26.6	23.2	78.1	68.0
Capital expenditures (including the effects of accruals)	68.3	84.5	216.8	232.6
Total assets	3,708.5	3,375.6	3,708.5	3,375.6
Short-term borrowings	40.0	76.0	40.0	76.0
Goodwill	182.1	182.1	182.1	182.1
Corporate & Other
Segment Reporting Information [Line Items]
Revenues, before intersegment effect	3.6	6.1	8.1	7.2
Cost of sales	(158.8)	44.7	(13.0)	219.7
Operating income	103.8	(40.0)	(75.2)	(221.9)
Income (loss) from equity investees	0.0	0.0	0.0	0.0
Loss on extinguishments of debt				(6.1)
Other non-operating (expense) income, net	(6.8)	(1.0)	(20.1)	11.3
Earnings (loss) before interest expense and income taxes	97.0	(41.0)	(95.3)	(216.7)
Interest expense	(7.4)	0.0	(24.9)	(0.2)
Income (loss) before income taxes	89.6	(41.0)	(120.2)	(216.9)
Noncontrolling interests’ net income (loss)	0.0	(3.8)	0.0	(49.3)
Depreciation and amortization	0.8	0.3	1.3	0.7
Capital expenditures (including the effects of accruals)	0.1	0.0	0.1	0.8
Total assets	240.3	358.1	240.3	358.1
Short-term borrowings	0.0	0.0	0.0	0.0
Goodwill	$ 0.0	$ 0.0	$ 0.0	0.0
Corporate & Other | AmeriGas Propane
Segment Reporting Information [Line Items]
Loss on extinguishments of debt				0.0
Corporate & Other | UGI International
Segment Reporting Information [Line Items]
Loss on extinguishments of debt				(6.1)
Corporate & Other | Midstream & Marketing
Segment Reporting Information [Line Items]
Loss on extinguishments of debt				$ 0.0