Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
Dec. 31, 2017	Dec. 31, 2016
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	$ 3,740.9
Other comprehensive (loss) income before reclassification adjustments (after-tax)	21.9	$ (58.6)
Amounts reclassified from AOCI:
Reclassification adjustments (pre-tax)	0.1	(5.0)
Reclassification adjustments tax (benefit) expense	(0.1)	1.5
Reclassification adjustments (after-tax)	0.0	(3.5)
Other comprehensive (loss) income attributable to UGI	21.9	(62.1)
Balance, end of period	4,082.1	3,733.1
Postretirement Benefit Plans
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	(19.2)	(29.1)
Other comprehensive (loss) income before reclassification adjustments (after-tax)	0.0	0.0
Amounts reclassified from AOCI:
Reclassification adjustments (pre-tax)	0.6	1.6
Reclassification adjustments tax (benefit) expense	(0.2)	(0.6)
Reclassification adjustments (after-tax)	0.4	1.0
Other comprehensive (loss) income attributable to UGI	0.4	1.0
Balance, end of period	(18.8)	(28.1)
Derivative Instruments
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	(21.4)	(13.4)
Other comprehensive (loss) income before reclassification adjustments (after-tax)	(0.4)	12.3
Amounts reclassified from AOCI:
Reclassification adjustments (pre-tax)	(0.5)	(6.6)
Reclassification adjustments tax (benefit) expense	0.1	2.1
Reclassification adjustments (after-tax)	(0.4)	(4.5)
Other comprehensive (loss) income attributable to UGI	(0.8)	7.8
Balance, end of period	(22.2)	(5.6)
Foreign Currency
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	(52.8)	(112.2)
Other comprehensive (loss) income before reclassification adjustments (after-tax)	22.3	(70.9)
Amounts reclassified from AOCI:
Reclassification adjustments (pre-tax)	0.0	0.0
Reclassification adjustments tax (benefit) expense	0.0	0.0
Reclassification adjustments (after-tax)	0.0	0.0
Other comprehensive (loss) income attributable to UGI	22.3	(70.9)
Balance, end of period	(30.5)	(183.1)
Total
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	(93.4)	(154.7)
Amounts reclassified from AOCI:
Balance, end of period	$ (71.5)	$ (216.8)

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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