Accumulated Other Comprehensive Loss (Reclassification) (Details) - USD ($) $ in Millions			3 Months Ended		9 Months Ended
		May 01, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of sales			$ 1,466.0	$ 1,545.4	$ 4,484.7	$ 4,623.7
Gain on exchange of equity affiliate investments		$ (29.1)	(29.1)	0.0	(29.1)	0.0
Other income/expense, net			(14.7)	(5.8)	(33.7)	(43.2)
Interest expense			34.2	34.9	106.9	95.1
Net Income Attributable to Air Products			(488.0)	(473.9)	(1,256.8)	(1,044.9)
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/Cost of sales			0.0	1.9	0.4	6.9
Other income/expense, net			(16.9)	(22.4)	8.9	(37.6)
Interest expense			3.8	2.8	11.4	6.3
Net Income Attributable to Air Products			(13.1)	(17.7)	20.7	(24.4)
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	0.0	0.0	3.1
Gain on exchange of equity affiliate investments	[2]		(2.6)	0.0	(2.6)	0.0
Net Income Attributable to Air Products			(2.6)	0.0	(2.6)	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	[3]		$ 14.8	$ 26.0	$ 48.7	$ 75.5

[1] The fiscal year 2018 impact relates to an equipment sale resulting from the termination of a contract in the Industrial Gases – Asia segment during the first quarter.

[2] The fiscal year 2019 impact relates to a net gain on the exchange of two equity affiliates with a joint venture partner. Refer to Note 6, Acquisitions, for additional information.

[3] 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 11, Retirement Benefits, for additional information.