Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period			$ 3,740.9
Other comprehensive income (loss) before reclassification adjustments (after-tax)	$ (78.3)	$ 68.9	(22.1)	$ 27.6
Amounts reclassified from AOCI:
Reclassification adjustments (pre-tax)	1.2	(0.1)	6.0	(12.3)
Reclassification adjustments tax (benefit) expense	(0.4)	(0.2)	(2.1)	3.5
Reclassification adjustments (after-tax)	0.8	(0.3)	3.9	(8.8)
Other comprehensive income (loss) attributable to UGI	(77.5)	68.6	(18.2)	18.8
Balance, end of period	4,227.8	3,841.1	4,227.8	3,841.1
Postretirement Benefit Plans
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	(18.5)	(27.7)	(19.2)	(29.1)
Other comprehensive income (loss) before reclassification adjustments (after-tax)	0.0	0.0	0.0	0.0
Amounts reclassified from AOCI:
Reclassification adjustments (pre-tax)	0.8	(0.1)	1.8	2.2
Reclassification adjustments tax (benefit) expense	(0.2)	0.0	(0.5)	(0.9)
Reclassification adjustments (after-tax)	0.6	(0.1)	1.3	1.3
Other comprehensive income (loss) attributable to UGI	0.6	(0.1)	1.3	1.3
Balance, end of period	(17.9)	(27.8)	(17.9)	(27.8)
Derivative Instruments
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	(21.0)	(11.5)	(21.4)	(13.4)
Other comprehensive income (loss) before reclassification adjustments (after-tax)	3.7	(6.6)	1.7	5.2
Amounts reclassified from AOCI:
Reclassification adjustments (pre-tax)	0.4	0.0	4.2	(14.5)
Reclassification adjustments tax (benefit) expense	(0.2)	(0.2)	(1.6)	4.4
Reclassification adjustments (after-tax)	0.2	(0.2)	2.6	(10.1)
Other comprehensive income (loss) attributable to UGI	3.9	(6.8)	4.3	(4.9)
Balance, end of period	(17.1)	(18.3)	(17.1)	(18.3)
Foreign Currency
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	5.4	(165.3)	(52.8)	(112.2)
Other comprehensive income (loss) before reclassification adjustments (after-tax)	(82.0)	75.5	(23.8)	22.4
Amounts reclassified from AOCI:
Reclassification adjustments (pre-tax)	0.0	0.0	0.0	0.0
Reclassification adjustments tax (benefit) expense	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	(82.0)	75.5	(23.8)	22.4
Balance, end of period	(76.6)	(89.8)	(76.6)	(89.8)
Total
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	(34.1)	(204.5)	(93.4)	(154.7)
Amounts reclassified from AOCI:
Balance, end of period	$ (111.6)	$ (135.9)	$ (111.6)	$ (135.9)

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Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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