Accumulated Other Comprehensive Loss (Rollforward) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 13,071.9	$ 11,929.8	$ 12,443.1	$ 11,388.3
Other comprehensive loss before reclassifications	(149.8)		279.7
Amounts reclassified from AOCL	54.3		71.3
Total Other Comprehensive Loss	(95.5)	(421.4)	351.0	(119.2)
Amount attributable to noncontrolling interests	15.6	(31.8)	35.3	(16.6)
Ending balance	13,134.8	11,723.7	13,134.8	11,723.7
Derivatives qualifying as hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(46.7)		(54.5)
Other comprehensive loss before reclassifications	(5.2)		8.6
Amounts reclassified from AOCL	36.0		34.7
Total Other Comprehensive Loss	30.8		43.3
Amount attributable to noncontrolling interests	18.8		23.5
Ending balance	(34.7)		(34.7)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(742.1)		(1,142.8)
Other comprehensive loss before reclassifications	(144.6)		271.1
Amounts reclassified from AOCL	0.0		0.0
Total Other Comprehensive Loss	(144.6)		271.1
Amount attributable to noncontrolling interests	(3.2)		11.8
Ending balance	(883.5)		(883.5)
Pension and postretirement benefits
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(924.5)		(942.8)
Other comprehensive loss before reclassifications	0.0		0.0
Amounts reclassified from AOCL	18.3		36.6
Total Other Comprehensive Loss	18.3		36.6
Amount attributable to noncontrolling interests	0.0		0.0
Ending balance	(906.2)		(906.2)
AOCL attributable to Air Products
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(1,713.3)	(2,088.6)	(2,140.1)	(2,375.6)
Total Other Comprehensive Loss	(111.1)	(389.6)	315.7	(102.6)
Ending balance	$ (1,824.4)	$ (2,478.2)	$ (1,824.4)	$ (2,478.2)