Segment Information - Schedule of Segment Reporting Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2018
Segment Reporting Information [Line Items]
Revenues	$ 2,606.1	$ 2,812.0	$ 4,806.3	$ 4,937.2
Cost of sales	1,426.9	1,560.2	2,851.9	2,697.6
Segment profit:
Operating income (loss)	538.8	591.0	706.5	986.0
Income from equity investees	1.6	0.7	3.1	1.7
Loss on extinguishments of debt	0.0	0.0	(6.1)	0.0
Other non-operating income, net	7.9	(12.5)	16.9	(20.5)
Interest expense	(61.0)	(58.1)	(121.2)	(116.3)
Income (loss) before income taxes	487.3	521.1	599.2	850.9
Noncontrolling interests’ net income (loss)	151.3	131.7	175.6	200.0
Depreciation and amortization	108.9	112.2	220.1	222.5
Capital expenditures (including the effects of accruals)	151.2	110.1	313.0	238.6
Total assets	12,350.9	12,445.3	12,350.9	12,445.3	$ 11,980.9
Short-term borrowings	341.0	302.8	341.0	302.8	424.9
Goodwill	3,147.8	3,218.1	3,147.8	3,218.1	$ 3,160.4
Eliminations
Segment Reporting Information [Line Items]
Revenues	(124.8)	(188.9)	(236.4)	(286.0)
Cost of sales	(123.6)	(187.9)	(234.4)	(283.9)
Segment profit:
Operating income (loss)	(0.4)	0.3	0.0	0.5
Income from equity investees	0.0	0.0	0.0	0.0
Loss on extinguishments of debt			0.0
Other non-operating income, net		0.0	0.0	0.0
Interest expense	0.0	0.0	0.0	0.0
Income (loss) before income taxes	(0.4)	0.3	0.0	0.5
Noncontrolling interests’ net income (loss)	0.0	0.0	0.0	0.0
Depreciation and amortization	(0.1)	(0.1)	(0.1)	(0.1)
Capital expenditures (including the effects of accruals)	0.0	0.0	0.0	0.0
Total assets	(121.5)	(59.4)	(121.5)	(59.4)
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	98.8	129.0	185.7	207.2
Eliminations | UGI Utilities
Segment Reporting Information [Line Items]
Revenues	25.3	58.7	48.9	76.4
Corporate, Intersegment Eliminations & Other
Segment Reporting Information [Line Items]
Revenues	0.7	1.2	1.8	2.4
Operating Segments | AmeriGas Propane
Segment Reporting Information [Line Items]
Revenues	971.6	1,040.3	1,791.8	1,827.6
Cost of sales	435.2	483.7	813.7	849.8
Segment profit:
Operating income (loss)	246.4	266.6	413.0	414.5
Income from equity investees	0.0	0.0	0.0	0.0
Loss on extinguishments of debt			0.0
Other non-operating income, net	0.0	0.0	0.0	0.0
Interest expense	(42.2)	(41.0)	(84.6)	(81.6)
Income (loss) before income taxes	204.2	225.6	328.4	332.9
Partnership Adjusted EBITDA	290.3	309.5	500.9	503.6
Noncontrolling interests’ net income (loss)	138.7	155.7	220.2	223.7
Depreciation and amortization	44.3	45.2	90.0	92.6
Capital expenditures (including the effects of accruals)	25.8	23.6	56.8	47.2
Total assets	3,978.1	4,149.8	3,978.1	4,149.8
Short-term borrowings	236.0	154.5	236.0	154.5
Goodwill	2,003.1	2,001.3	2,003.1	2,001.3
Operating Segments | UGI International
Segment Reporting Information [Line Items]
Revenues	783.2	909.6	1,493.9	1,693.8
Cost of sales	444.7	541.1	893.3	1,025.9
Segment profit:
Operating income (loss)	126.9	132.0	185.2	225.2
Income from equity investees	0.1	(0.1)	0.1	(0.3)
Loss on extinguishments of debt			(6.1)
Other non-operating income, net	3.1	(9.2)	3.8	(14.0)
Interest expense	(6.1)	(5.2)	(11.5)	(10.8)
Income (loss) before income taxes	124.0	117.5	171.5	200.1
Noncontrolling interests’ net income (loss)	0.2	(1.2)	0.3	(1.5)
Depreciation and amortization	30.6	34.9	62.0	67.1
Capital expenditures (including the effects of accruals)	22.1	26.1	49.9	47.8
Total assets	3,229.6	3,562.3	3,229.6	3,562.3
Short-term borrowings	0.0	3.3	0.0	3.3
Goodwill	944.8	1,023.2	944.8	1,023.2
Operating Segments | Midstream & Marketing
Segment Reporting Information [Line Items]
Revenues	542.4		1,001.8
Revenues, before intersegment effect	443.6	436.2	816.1	686.0
Cost of sales	449.3	418.6	826.8	657.6
Segment profit:
Operating income (loss)	51.3	107.6	92.4	161.0
Income from equity investees	1.5	0.8	3.0	2.0
Loss on extinguishments of debt			0.0
Other non-operating income, net	0.0	(0.1)	0.0	(1.2)
Interest expense	(0.5)	(0.7)	(1.0)	(1.6)
Income (loss) before income taxes	52.3	107.6	94.4	160.2
Noncontrolling interests’ net income (loss)	0.0	0.0	0.0	0.0
Depreciation and amortization	11.5	10.8	23.0	20.9
Capital expenditures (including the effects of accruals)	32.3	4.3	57.4	15.6
Total assets	1,500.9	1,347.7	1,500.9	1,347.7
Short-term borrowings	0.0	10.0	0.0	10.0
Goodwill	17.8	11.5	17.8	11.5
Operating Segments | UGI Utilities
Segment Reporting Information [Line Items]
Revenues	429.6		752.3
Revenues, before intersegment effect	404.3	424.6	703.4	730.0
Cost of sales	218.0	257.3	377.5	409.1
Segment profit:
Operating income (loss)	119.9	135.7	196.9	232.6
Income from equity investees	0.0	0.0	0.0	0.0
Loss on extinguishments of debt			0.0
Other non-operating income, net	0.4	(0.6)	0.8	(1.2)
Interest expense	(12.2)	(11.1)	(23.9)	(22.0)
Income (loss) before income taxes	108.1	124.0	173.8	209.4
Noncontrolling interests’ net income (loss)	0.0	0.0	0.0	0.0
Depreciation and amortization	22.3	21.1	44.8	41.5
Capital expenditures (including the effects of accruals)	70.8	55.1	148.1	126.8
Total assets	3,438.4	3,204.0	3,438.4	3,204.0
Short-term borrowings	105.0	135.0	105.0	135.0
Goodwill	182.1	182.1	182.1	182.1
Corporate & Other
Segment Reporting Information [Line Items]
Revenues	4.1		2.9
Revenues, before intersegment effect	3.4	1.3	1.1	(0.2)
Cost of sales	3.3	47.4	175.0	39.1
Segment profit:
Operating income (loss)	(5.3)	(51.2)	(181.0)	(47.8)
Income from equity investees	0.0	0.0	0.0	0.0
Loss on extinguishments of debt			0.0
Other non-operating income, net	4.4	(2.6)	12.3	(4.1)
Interest expense	0.0	(0.1)	(0.2)	(0.3)
Income (loss) before income taxes	(0.9)	(53.9)	(168.9)	(52.2)
Noncontrolling interests’ net income (loss)	12.4	(22.8)	(44.9)	(22.2)
Depreciation and amortization	0.3	0.3	0.4	0.5
Capital expenditures (including the effects of accruals)	0.2	1.0	0.8	1.2
Total assets	325.4	240.9	325.4	240.9
Short-term borrowings	0.0	0.0	0.0	0.0
Goodwill	$ 0.0	$ 0.0	$ 0.0	$ 0.0