Accumulated Other Comprehensive Loss (Rollforward) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 13,134.8	$ 11,723.7	$ 12,443.1	$ 11,388.3
Other comprehensive income before reclassifications	137.2		416.9
Amounts reclassified from AOCL	6.7		78.0
Total Other Comprehensive Income	143.9	126.9	494.9	7.7
Amount attributable to noncontrolling interests	1.4	1.8	36.7	(14.8)
Ending balance	13,491.6	12,023.4	13,491.6	12,023.4
Derivatives qualifying as hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(34.7)		(54.5)
Other comprehensive income before reclassifications	8.5		17.1
Amounts reclassified from AOCL	(12.0)		22.7
Total Other Comprehensive Income	(3.5)		39.8
Amount attributable to noncontrolling interests	(5.4)		18.1
Ending balance	(32.8)		(32.8)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(883.5)		(1,142.8)
Other comprehensive income before reclassifications	128.7		399.8
Amounts reclassified from AOCL	0.0		0.0
Total Other Comprehensive Income	128.7		399.8
Amount attributable to noncontrolling interests	6.6		18.4
Ending balance	(761.4)		(761.4)
Pension and postretirement benefits
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(906.2)		(942.8)
Other comprehensive income before reclassifications	0.0		0.0
Amounts reclassified from AOCL	18.7		55.3
Total Other Comprehensive Income	18.7		55.3
Amount attributable to noncontrolling interests	0.2		0.2
Ending balance	(887.7)		(887.7)
AOCL attributable to Air Products
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(1,824.4)	(2,478.2)	(2,140.1)	(2,375.6)
Total Other Comprehensive Income	142.5	125.1	458.2	22.5
Ending balance	$ (1,681.9)	$ (2,353.1)	$ (1,681.9)	$ (2,353.1)