Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
AOCI Including Portion Attributable to NCI [Roll Forward]:
Balance, beginning of year	$ 3,595.0	$ 3,565.6
Other comprehensive (loss) income before reclassification adjustments (after-tax)	67.6	(34.2)	$ (98.5)
Amounts reclassified from AOCI and noncontrolling interests:
Reclassification adjustments (pre-tax)	(8.3)	(10.5)	6.6
Reclassification adjustments tax (benefit) expense	2.0	4.6	(3.6)
Reclassification adjustments (after-tax)	6.3	5.9	(3.0)
Other comprehensive income (loss)	61.3	(40.1)	(95.5)
Add comprehensive loss attributable to noncontrolling interests, principally in AmeriGas Partners			2.1
Other comprehensive loss attributable to UGI	61.3	(40.1)	(93.4)
Balance, end of year	3,740.9	3,595.0	3,565.6
Postretirement Benefit Plans
AOCI Including Portion Attributable to NCI [Roll Forward]:
Balance, beginning of year	(29.1)	(20.4)	(20.6)
Other comprehensive (loss) income before reclassification adjustments (after-tax)	6.5	(10.9)	(1.2)
Amounts reclassified from AOCI and noncontrolling interests:
Reclassification adjustments (pre-tax)	5.5	2.6	2.2
Reclassification adjustments tax (benefit) expense	(2.1)	(0.4)	(0.8)
Reclassification adjustments (after-tax)	(3.4)	(2.2)	(1.4)
Other comprehensive income (loss)			0.2
Add comprehensive loss attributable to noncontrolling interests, principally in AmeriGas Partners			0.0
Other comprehensive loss attributable to UGI	9.9	(8.7)	0.2
Balance, end of year	(19.2)	(29.1)	(20.4)
Derivative Instruments
AOCI Including Portion Attributable to NCI [Roll Forward]:
Balance, beginning of year	(13.4)	11.2	(9.3)
Other comprehensive (loss) income before reclassification adjustments (after-tax)	1.7	(16.5)	16.8
Amounts reclassified from AOCI and noncontrolling interests:
Reclassification adjustments (pre-tax)	(13.8)	(13.1)	4.4
Reclassification adjustments tax (benefit) expense	4.1	5.0	(2.8)
Reclassification adjustments (after-tax)	9.7	8.1	(1.6)
Other comprehensive income (loss)			18.4
Add comprehensive loss attributable to noncontrolling interests, principally in AmeriGas Partners			2.1
Other comprehensive loss attributable to UGI	(8.0)	(24.6)	20.5
Balance, end of year	(21.4)	(13.4)	11.2
Foreign Currency
AOCI Including Portion Attributable to NCI [Roll Forward]:
Balance, beginning of year	(112.2)	(105.4)	8.7
Other comprehensive (loss) income before reclassification adjustments (after-tax)	59.4	(6.8)	(114.1)
Amounts reclassified from AOCI and noncontrolling interests:
Reclassification adjustments (pre-tax)	0.0	0.0	0.0
Reclassification adjustments tax (benefit) expense	0.0	0.0	0.0
Reclassification adjustments (after-tax)	0.0	0.0	0.0
Other comprehensive income (loss)			(114.1)
Add comprehensive loss attributable to noncontrolling interests, principally in AmeriGas Partners			0.0
Other comprehensive loss attributable to UGI	59.4	(6.8)	(114.1)
Balance, end of year	(52.8)	(112.2)	(105.4)
Accumulated Other Comprehensive Income (Loss)
AOCI Including Portion Attributable to NCI [Roll Forward]:
Balance, beginning of year	(154.7)	(114.6)	(21.2)
Amounts reclassified from AOCI and noncontrolling interests:
Balance, end of year	$ (93.4)	$ (154.7)	$ (114.6)