Segment Information - Schedule of Segment Reporting Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2017
Segment Reporting Information [Line Items]
Revenues	$ 2,812.0	$ 2,173.8	$ 4,937.2	$ 3,853.3
Cost of sales	1,560.2	1,071.2	2,697.6	1,718.6
Segment profit:
Operating income (loss)	589.5	513.2	981.3	979.4
Income (loss) from equity investees	0.7	2.3	1.7	2.1
(Losses) gains on foreign currency contracts, net	(11.0)	(1.2)	(15.8)	0.1
Loss on extinguishments of debt	0.0	(22.1)	0.0	(55.3)
Interest expense	(58.1)	(55.8)	(116.3)	(111.2)
Income (loss) before income taxes	521.1	436.4	850.9	815.1
Noncontrolling interests’ net income (loss)	131.7	91.9	200.0	152.1
Depreciation and amortization	112.2	99.3	222.5	197.4
Capital expenditures (including the effects of accruals)	110.1	126.2	238.6	299.8
Total assets	12,445.3	11,385.5	12,445.3	11,385.5	$ 11,582.2
Short-term borrowings	302.8	50.1	302.8	50.1	366.9
Goodwill	3,218.1	2,948.4	3,218.1	2,948.4	$ 3,107.2
Cost-method Investments, Other than Temporary Impairment		7.0	7.0
Eliminations
Segment Reporting Information [Line Items]
Revenues	(188.9)	(95.8)	(286.0)	(164.3)
Cost of sales	(187.9)	(94.9)	(283.9)	(162.6)
Segment profit:
Operating income (loss)	0.3	0.0	0.5	0.1
Income (loss) from equity investees	0.0	0.0	0.0	0.0
(Losses) gains on foreign currency contracts, net	0.0	0.0	0.0	0.0
Loss on extinguishments of debt		0.0		0.0
Interest expense	0.0	0.0	0.0	0.0
Income (loss) before income taxes	0.3	0.0	0.5	0.1
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	(59.4)	(58.6)	(59.4)	(58.6)
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	129.0	76.2	207.2	136.4
Eliminations | UGI Utilities
Segment Reporting Information [Line Items]
Revenues	58.7	18.8	76.4	26.3
Corporate, Intersegment Eliminations & Other
Segment Reporting Information [Line Items]
Revenues	1.2	0.8	2.4	1.6
Operating Segments | AmeriGas Propane
Segment Reporting Information [Line Items]
Revenues	1,040.3	863.6	1,827.6	1,540.8
Cost of sales	483.7	355.8	849.8	616.5
Segment profit:
Operating income (loss)	266.6	227.3	414.5	369.2
Income (loss) from equity investees	0.0	0.0	0.0	0.0
(Losses) gains on foreign currency contracts, net	0.0	0.0	0.0	0.0
Loss on extinguishments of debt	0.0	(22.1)	0.0	(55.3)
Interest expense	(41.0)	(40.0)	(81.6)	(80.0)
Income (loss) before income taxes	225.6	165.2	332.9	233.9
Partnership Adjusted EBITDA	309.5	271.2	503.6	456.3
Noncontrolling interests’ net income (loss)	155.7	112.7	223.7	153.9
Depreciation and amortization	45.2	45.0	92.6	89.6
Capital expenditures (including the effects of accruals)	23.6	27.2	47.2	53.6
Total assets	4,149.8	4,238.1	4,149.8	4,238.1
Short-term borrowings	154.5	0.0	154.5	0.0
Goodwill	2,001.3	1,981.2	2,001.3	1,981.2
Operating Segments | UGI International
Segment Reporting Information [Line Items]
Revenues	909.6	620.7	1,693.8	1,159.8
Cost of sales	541.1	313.1	1,025.9	571.1
Segment profit:
Operating income (loss)	131.8	121.0	224.9	209.9
Income (loss) from equity investees	(0.1)	(0.1)	(0.3)	(0.3)
(Losses) gains on foreign currency contracts, net	(9.0)	0.1	(13.7)	0.2
Loss on extinguishments of debt		0.0		0.0
Interest expense	(5.2)	(4.8)	(10.8)	(9.6)
Income (loss) before income taxes	117.5	116.2	200.1	200.2
Noncontrolling interests’ net income (loss)	(1.2)	0.1	(1.5)	0.3
Depreciation and amortization	34.9	27.6	67.1	55.5
Capital expenditures (including the effects of accruals)	26.1	21.5	47.8	43.0
Total assets	3,562.3	2,804.7	3,562.3	2,804.7
Short-term borrowings	3.3	1.6	3.3	1.6
Goodwill	1,023.2	773.6	1,023.2	773.6
Operating Segments | Midstream & Marketing
Segment Reporting Information [Line Items]
Revenues	436.2	347.5	686.0	557.1
Cost of sales	418.6	309.8	657.6	501.6
Segment profit:
Operating income (loss)	107.5	82.1	159.8	131.8
Income (loss) from equity investees	0.8	2.4	2.0	2.4
(Losses) gains on foreign currency contracts, net	0.0	0.0	0.0	0.0
Loss on extinguishments of debt		0.0		0.0
Interest expense	(0.7)	(0.7)	(1.6)	(1.3)
Income (loss) before income taxes	107.6	83.8	160.2	132.9
Noncontrolling interests’ net income (loss)	0.0	0.0	0.0	0.0
Depreciation and amortization	10.8	8.8	20.9	16.8
Capital expenditures (including the effects of accruals)	4.3	20.8	15.6	82.3
Total assets	1,347.7	1,200.7	1,347.7	1,200.7
Short-term borrowings	10.0	0.0	10.0	0.0
Goodwill	11.5	11.5	11.5	11.5
Operating Segments | UGI Utilities
Segment Reporting Information [Line Items]
Revenues	424.6	341.2	730.0	595.1
Cost of sales	257.3	164.5	409.1	274.0
Segment profit:
Operating income (loss)	135.1	116.4	231.4	198.6
Income (loss) from equity investees	0.0	0.0	0.0	0.0
(Losses) gains on foreign currency contracts, net	0.0	0.0	0.0	0.0
Loss on extinguishments of debt		0.0		0.0
Interest expense	(11.1)	(10.3)	(22.0)	(20.3)
Income (loss) before income taxes	124.0	106.1	209.4	178.3
Noncontrolling interests’ net income (loss)	0.0	0.0	0.0	0.0
Depreciation and amortization	21.1	17.7	41.5	35.1
Capital expenditures (including the effects of accruals)	55.1	56.5	126.8	120.6
Total assets	3,204.0	2,909.7	3,204.0	2,909.7
Short-term borrowings	135.0	48.5	135.0	48.5
Goodwill	182.1	182.1	182.1	182.1
Corporate & Other
Segment Reporting Information [Line Items]
Revenues	1.3	0.8	(0.2)	0.5
Cost of sales	47.4	22.9	39.1	(82.0)
Segment profit:
Operating income (loss)	(51.8)	(33.6)	(49.8)	69.8
Income (loss) from equity investees	0.0	0.0	0.0	0.0
(Losses) gains on foreign currency contracts, net	(2.0)	(1.3)	(2.1)	(0.1)
Loss on extinguishments of debt		0.0		0.0
Interest expense	(0.1)	0.0	(0.3)	0.0
Income (loss) before income taxes	(53.9)	(34.9)	(52.2)	69.7
Noncontrolling interests’ net income (loss)	(22.8)	(20.9)	(22.2)	(2.1)
Depreciation and amortization	0.3	0.3	0.5	0.5
Capital expenditures (including the effects of accruals)	1.0	0.2	1.2	0.3
Total assets	240.9	290.9	240.9	290.9
Short-term borrowings	0.0	0.0	0.0	0.0
Goodwill	0.0	0.0	0.0	0.0
Gains (losses) on unsettled commodity derivative instruments, net	$ (48.1)	$ (23.9)	$ (41.5)	$ 81.6