Accumulated Other Comprehensive Loss (Reclassification) (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ 36.7	$ 18.7
Other non-operating income (expense), net	(18.6)	(9.1)
Net Income Attributable to Air Products	(482.0)	(475.6)
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/Cost of sales	0.2	0.0
Interest expense	0.9	0.7
Other non-operating income (expense), net	(2.4)	(4.3)
Net Income Attributable to Air Products	(1.3)	(3.6)
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	$ 19.7