Accumulated Other Comprehensive Loss (Reclassification) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income/expense, net	$ (15.7)	$ (14.7)	$ (36.1)	$ (33.7)
Interest expense	32.1	34.2	70.1	106.9
Other non-operating income (expense), net	(8.1)	(17.6)	(24.3)	(49.8)
Net Income Attributable to Air Products	(446.5)	(488.0)	(1,399.9)	(1,256.8)
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	0.0		(0.7)
Other income/expense, net	0.0		0.0
Interest expense	0.7		2.1
Other non-operating income (expense), net	(23.9)		(45.2)
Net Income Attributable to Air Products	(23.2)		(43.8)
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		0.0		0.4
Other income/expense, net		(16.9)		8.9
Interest expense		3.8		11.4
Other non-operating income (expense), net		0.0		0.0
Net Income Attributable to Air Products		(13.1)		20.7
Reclassification out of Accumulated Other Comprehensive Income | Currency Translation Adjustment
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net Income Attributable to Air Products	0.0	(2.6)	0.0	(2.6)
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	$ 19.8	$ 14.8	$ 60.7	$ 48.7