Accumulated Other Comprehensive Loss (Rollforward) (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 10,185.5	$ 7,213.4	$ 7,381.1
Other comprehensive income (loss) before reclassifications	(19.3)	340.9	(311.5)
Amounts reclassified from AOCL	105.8	192.2	53.9
Total Other Comprehensive Income (Loss)	86.5	533.1	(257.6)
Spin-off of Versum		11.5
Amount attributable to noncontrolling interest	(19.0)	3.7	4.8
Ending Balance	11,176.3	10,185.5	7,213.4
Derivatives qualifying as hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(53.1)	(65.0)	(42.9)
Other comprehensive income (loss) before reclassifications	45.9	(12.6)	13.7
Amounts reclassified from AOCL	(30.4)	24.2	(36.0)
Total Other Comprehensive Income (Loss)	15.5	11.6	(22.3)
Spin-off of Versum		0.2
Amount attributable to noncontrolling interest	0.0	(0.1)	(0.2)
Ending Balance	(37.6)	(53.1)	(65.0)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(787.1)	(949.3)	(956.5)
Other comprehensive income (loss) before reclassifications	(244.6)	101.9	9.9
Amounts reclassified from AOCL	3.1	57.3	2.7
Total Other Comprehensive Income (Loss)	(241.5)	159.2	12.6
Spin-off of Versum		6.0
Amount attributable to noncontrolling interest	(18.8)	3.0	5.4
Ending Balance	(1,009.8)	(787.1)	(949.3)
Pension and postretirement benefits
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(1,007.2)	(1,374.0)	(1,126.5)
Other comprehensive income (loss) before reclassifications	179.4	251.6	(335.1)
Amounts reclassified from AOCL	133.1	110.7	87.2
Total Other Comprehensive Income (Loss)	312.5	362.3	(247.9)
Spin-off of Versum		5.3
Amount attributable to noncontrolling interest	(0.2)	0.8	(0.4)
Ending Balance	(694.5)	(1,007.2)	(1,374.0)
AOCL attributable to Air Products
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(1,847.4)	(2,388.3)	(2,125.9)
Total Other Comprehensive Income (Loss)	105.5	529.4	(262.4)
Ending Balance	$ (1,741.9)	$ (1,847.4)	$ (2,388.3)

The release of accumulated other comprehensive loss as a result of spin-off transaction.

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

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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Amount after tax of other comprehensive income (loss) attributable to noncontrolling interests.

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Amount after tax of reclassification adjustments of other comprehensive income (loss).

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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 of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

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