Accumulated Other Comprehensive Loss (Reclassification) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income (expense), net		$ (26.3)	$ (11.1)	$ (73.0)	$ (29.3)
Interest expense		29.8	35.1	89.8	83.0
Cost reduction and asset actions		42.7	13.2	103.0	23.9
Income (loss) from discontinued operations, net of tax		(2.3)	98.4	1,871.5	(567.0)
Net Income (Loss) Attributable to Air Products		(101.9)	(346.8)	(2,531.7)	(237.1)
Reclassification out of Accumulated Other Comprehensive Income [Member] | (Gain) Loss on Cash Flow Hedges, net of tax [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Sales/Cost of sales		4.3	1.0	10.1	2.4
Other income (expense), net		(29.0)	5.5	(2.4)	(30.5)
Interest expense		1.1	3.5	0.1	7.7
Net Income (Loss) Attributable to Air Products		(23.6)	10.0	7.8	(20.4)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Currency Translation Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost reduction and asset actions	[1]	8.2	0.0	8.2	0.0
Income (loss) from discontinued operations, net of tax	[2]	0.0	(0.1)	49.1	2.7
Net Income (Loss) Attributable to Air Products		(8.2)	0.1	(57.3)	(2.7)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Pension and Postretirement Benefits, net of tax [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net Income (Loss) Attributable to Air Products	[3]	$ 27.7	$ 21.6	$ 85.2	$ 65.4

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

[2] The fiscal year 2017 impact relates to the sale of PMD during the second quarter. The fiscal year 2016 impact primarily relates to the sale of an equity affiliate in the first quarter.

[3] The components include items such as prior service cost amortization, actuarial loss amortization, and settlements and are reflected in net periodic benefit cost. Refer to Note 12, Retirement Benefits.