Accumulated Other Comprehensive Loss (Reclassification) (Details) - USD ($) $ in Millions		3 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income/expense, net		$ (8.6)	$ (22.1)
Interest expense		37.3	29.8
Cost of sales		1,544.0	1,571.8
Net Income Attributable to Air Products		(347.5)	(154.6)
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		0.5	1.0
Other income/expense, net		(7.4)	(1.4)
Interest expense		3.8	1.2
Net Income Attributable to Air Products		(3.1)	0.8
Reclassification out of Accumulated Other Comprehensive Income | Currency Translation Adjustment
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of sales	[1]	0.0	3.1
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	[2]	$ 15.2	$ 22.9

[1] The fiscal year 2018 impact is reflected in "Cost of sales" on the consolidated income statements and relates to an equipment sale resulting from the termination of a contract in the Industrial Gases – Asia segment.

[2] The components of net periodic benefit cost reclassified out of AOCL include items such as prior service cost amortization, actuarial loss amortization, and settlements and are included in “Other non-operating income (expense), net” on the consolidated income statements. Refer to Note 9, Retirement Benefits, for additional information.