Accumulated Other Comprehensive Loss (Reclassification) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Sales	$ (2,502.0)	$ (2,216.3)	$ (4,877.2)	$ (4,471.0)
Cost of sales	(1,745.5)	(1,460.1)	(3,377.9)	(2,946.7)
Interest expense	(36.1)	(19.3)	(72.8)	(38.0)
Other non-operating income (expense), net	(16.8)	(7.1)	(35.4)	(16.2)
Net Income Attributable to Air Products	(473.1)	(477.8)	(955.1)	(953.4)
Reclassification out of Accumulated Other Comprehensive Income | (Gain) Loss on Cash Flow Hedges, net of tax
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Sales	0.1	(0.2)	0.2	(0.1)
Cost of sales	(1.4)	(0.5)	(1.3)	(0.6)
Interest expense	0.9	0.7	1.8	1.4
Other non-operating income (expense), net	36.4	(17.0)	34.0	(21.3)
Net Income Attributable to Air Products	36.0	(17.0)	34.7	(20.6)
Reclassification out of Accumulated Other Comprehensive Income | Pension and Postretirement Benefits, net of tax
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net Income Attributable to Air Products	$ 18.3	$ 21.2	$ 36.6	$ 40.9