Accumulated Other Comprehensive Loss (Reclassification) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Sales	$ (2,604.7)	$ (2,065.2)	$ (7,481.9)	$ (6,536.2)
Cost of sales	(1,801.9)	(1,344.9)	(5,179.8)	(4,291.6)
Interest expense	(35.6)	(32.1)	(108.4)	(70.1)
Other non-operating income (expense), net	(21.1)	(8.1)	(56.5)	(24.3)
Net Income Attributable to Air Products	(533.6)	(446.5)	(1,488.7)	(1,399.9)
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	0.0	0.0	0.2	(0.1)
Cost of sales	0.2	0.0	(1.1)	(0.6)
Interest expense	0.9	0.7	2.7	2.1
Other non-operating income (expense), net	(13.1)	(23.9)	20.9	(45.2)
Net Income Attributable to Air Products	(12.0)	(23.2)	22.7	(43.8)
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	$ 18.7	$ 19.8	$ 55.3	$ 60.7