Accumulated Other Comprehensive Loss (Reclassification) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income (expense), net									$ (65.4)	$ (49.3)	$ (50.2)
Interest expense									109.3	137.0	130.5
Other non-operating income (expense), net									(30.7)	(66.7)	(5.1)
Net income (loss) attributable to Air Products	$ (486.8)	$ (446.5)	$ (477.8)	$ (475.6)	$ (503.2)	$ (488.0)	$ (421.3)	$ (347.5)	(1,886.7)	(1,760.0)	(1,497.8)
Reclassification out of Accumulated Other Comprehensive Income | (Gain) Loss on Cash Flow Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Sales/Cost of sales									(1.0)
Other income (expense), net									0.0
Interest expense									2.8
Other non-operating income (expense), net									(59.5)
Net income (loss) attributable to Air Products									(57.7)
Reclassification out of Accumulated Other Comprehensive Income | (Gain) Loss on Cash Flow Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Sales/Cost of sales										0.6	7.1
Other income (expense), net										(3.0)	(42.6)
Interest expense										14.7	5.1
Other non-operating income (expense), net										0.0	0.0
Net income (loss) attributable to Air Products										12.3	(30.4)
Reclassification out of Accumulated Other Comprehensive Income | Currency Translation Adjustment
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income (loss) attributable to Air Products									0.0	(2.6)	3.1
Reclassification out of Accumulated Other Comprehensive Income | Pension and Postretirement Benefits
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income (loss) attributable to Air Products									$ 82.5	$ 63.2	$ 133.1