Accumulated Other Comprehensive Loss (Rollforward) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 11,723.7	$ 11,503.4	$ 11,388.3	$ 11,176.3
Other comprehensive income before reclassifications	130.3		(9.2)
Amounts reclassified from AOCL	(3.4)		16.9
Total Other Comprehensive Income (Loss)	126.9	(42.2)	7.7	(40.9)
Amount attributable to noncontrolling interests	1.8	(5.6)	(14.8)	(1.4)
Ending balance	12,023.4	11,726.6	12,023.4	11,726.6
Derivatives qualifying as hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(67.3)		(61.4)
Other comprehensive income before reclassifications	23.4		18.1
Amounts reclassified from AOCL	(23.2)		(43.8)
Total Other Comprehensive Income (Loss)	0.2		(25.7)
Amount attributable to noncontrolling interests	(1.6)		(21.6)
Ending balance	(65.5)		(65.5)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(1,494.5)		(1,356.9)
Other comprehensive income before reclassifications	106.9		(27.3)
Amounts reclassified from AOCL	0.0		0.0
Total Other Comprehensive Income (Loss)	106.9		(27.3)
Amount attributable to noncontrolling interests	3.4		6.8
Ending balance	(1,391.0)		(1,391.0)
Pension and postretirement benefits
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(916.4)		(957.3)
Other comprehensive income before reclassifications	0.0		0.0
Amounts reclassified from AOCL	19.8		60.7
Total Other Comprehensive Income (Loss)	19.8		60.7
Amount attributable to noncontrolling interests	0.0		0.0
Ending balance	(896.6)		(896.6)
AOCL attributable to Air Products
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(2,478.2)	(1,744.8)	(2,375.6)	(1,741.9)
Total Other Comprehensive Income (Loss)	125.1	(36.6)	22.5	(39.5)
Ending balance	$ (2,353.1)	$ (1,781.4)	$ (2,353.1)	$ (1,781.4)