Accumulated Other Comprehensive Loss (Reclassification) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended		12 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income/expense, net		$ (5.8)	$ (26.3)	$ (43.2)	$ (73.0)
Interest expense		34.9	29.8	95.1	89.8
Cost of sales		1,545.4	1,486.0	4,623.7	4,206.5
Cost reduction and asset actions		0.0	42.7	0.0	103.0	$ 151.4
Loss from discontinued operations, net of tax		(43.2)	2.3	(42.2)	(1,871.5)
Net Income Attributable to Air Products		(473.9)	(101.9)	(1,044.9)	(2,531.7)
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		1.9	4.3	6.9	10.1
Other income/expense, net		(22.4)	(29.0)	(37.6)	(2.4)
Interest expense		2.8	1.1	6.3	0.1
Net Income Attributable to Air Products		(17.7)	(23.6)	(24.4)	7.8
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	0.0	3.1	0.0
Cost reduction and asset actions	[2]	0.0	8.2	0.0	8.2
Loss from discontinued operations, net of tax	[3]	0.0	0.0	0.0	49.1
Net Income Attributable to Air Products		0.0	8.2	3.1	57.3
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	[4]	$ 26.0	$ 27.7	$ 75.5	$ 85.2

[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 2017 impact relates to the planned sale of a non-industrial gas hardgoods business in the Industrial Gases – Americas segment.

[3] The fiscal year 2017 impact relates to the sale of PMD during the second quarter.

[4] The components of net periodic benefit cost reclassified out of accumulated other comprehensive loss 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 13, Retirement Benefits, for additional information.