Accumulated Other Comprehensive Loss (Rollforward) (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 14,088.0	$ 12,443.1
Other comprehensive (loss) income before reclassifications	40.1
Amounts reclassified from AOCL	34.7
Total Other Comprehensive Income	74.8	446.5
Amount attributable to noncontrolling interests	11.2	19.7
Ending balance	14,375.6	13,071.9
Derivatives qualifying as hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(28.3)
Other comprehensive (loss) income before reclassifications	(0.5)
Amounts reclassified from AOCL	18.7
Total Other Comprehensive Income	18.2
Amount attributable to noncontrolling interests	7.4
Ending balance	(17.5)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(893.8)
Other comprehensive (loss) income before reclassifications	40.6
Amounts reclassified from AOCL	0.0
Total Other Comprehensive Income	40.6
Amount attributable to noncontrolling interests	3.8
Ending balance	(857.0)
Pension and postretirement benefits
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(593.8)
Other comprehensive (loss) income before reclassifications	0.0
Amounts reclassified from AOCL	16.0
Total Other Comprehensive Income	16.0
Amount attributable to noncontrolling interests	0.0
Ending balance	(577.8)
AOCL attributable to Air Products
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(1,515.9)	(2,140.1)
Total Other Comprehensive Income	63.6	426.8
Ending balance	$ (1,452.3)	$ (1,713.3)