Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period			$ 3,827.2
Other comprehensive (loss) income before reclassification adjustments (after-tax)	$ 20.0	$ 14.5	4.3	$ (30.6)
Amounts reclassified from AOCI:
Reclassification adjustments (pre-tax)	7.1	1.2	10.7	3.0
Reclassification adjustments tax benefit	(2.0)	(0.3)	(3.0)	(0.8)
Reclassification adjustments (after-tax)	5.1	0.9	7.7	2.2
Other comprehensive income (loss) attributable to UGI	25.1	15.4	12.0	(28.4)
Balance, end of period	4,135.4	4,173.7	4,135.4	4,173.7
Postretirement Benefit Plans
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	(24.4)	(13.3)	(25.7)	(11.0)
Other comprehensive (loss) income before reclassification adjustments (after-tax)	0.0	0.0	0.0	0.0
Amounts reclassified from AOCI:
Reclassification adjustments (pre-tax)	0.5	0.3	2.3	1.1
Reclassification adjustments tax benefit	(0.1)	(0.1)	(0.6)	(0.3)
Reclassification adjustments (after-tax)	0.4	0.2	1.7	0.8
Other comprehensive income (loss) attributable to UGI	0.4	0.2	1.7	0.8
Reclassification of stranded income tax effects related to TCJA				(2.9)
Balance, end of period	(24.0)	(13.1)	(24.0)	(13.1)
Derivative Instruments
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	(54.1)		(25.4)
Other comprehensive (loss) income before reclassification adjustments (after-tax)	(7.6)		(37.6)
Amounts reclassified from AOCI:
Reclassification adjustments (pre-tax)	6.6		8.4
Reclassification adjustments tax benefit	(1.9)		(2.4)
Reclassification adjustments (after-tax)	4.7		6.0
Other comprehensive income (loss) attributable to UGI	(2.9)		(31.6)
Balance, end of period	(57.0)		(57.0)
Derivative Instruments
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period		(21.8)		(16.1)
Other comprehensive (loss) income before reclassification adjustments (after-tax)		(1.6)		(4.3)
Amounts reclassified from AOCI:
Reclassification adjustments (pre-tax)		0.9		1.9
Reclassification adjustments tax benefit		(0.2)		(0.5)
Reclassification adjustments (after-tax)		0.7		1.4
Other comprehensive income (loss) attributable to UGI		(0.9)		(2.9)
Reclassification of stranded income tax effects related to TCJA				(3.7)
Balance, end of period		(22.7)		(22.7)
Foreign Currency
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	(151.2)	(125.7)	(165.5)	(83.3)
Other comprehensive (loss) income before reclassification adjustments (after-tax)	27.6	16.1	41.9	(26.3)
Amounts reclassified from AOCI:
Reclassification adjustments (pre-tax)	0.0	0.0	0.0	0.0
Reclassification adjustments tax benefit	0.0	0.0	0.0	0.0
Reclassification adjustments (after-tax)	0.0	0.0	0.0	0.0
Other comprehensive income (loss) attributable to UGI	27.6	16.1	41.9	(26.3)
Reclassification of stranded income tax effects related to TCJA				0.0
Balance, end of period	(123.6)	(109.6)	(123.6)	(109.6)
Total
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	(229.7)	(160.8)	(216.6)	(110.4)
Amounts reclassified from AOCI:
Reclassification of stranded income tax effects related to TCJA				(6.6)
Balance, end of period	$ (204.6)	$ (145.4)	$ (204.6)	$ (145.4)