Accumulated Other Comprehensive Loss (Reclassification) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income (expense), net		$ (22.0)	$ (13.3)	$ (46.7)	$ (18.2)
Interest expense		30.5	25.7	60.0	47.9
Income (Loss) From Discontinued Operations, net of tax		1,825.6	(750.2)	1,873.8	(665.4)
Net Income (Loss) Attributable to Air Products		(2,130.0)	473.3	(2,429.8)	109.7
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		1.2	0.5	5.8	1.4
Other income (expense), net		5.5	(13.6)	26.6	(36.0)
Interest expense		(0.9)	2.0	(1.0)	4.2
Net Income (Loss) Attributable to Air Products		5.8	(11.1)	31.4	(30.4)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Currency Translation Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (Loss) From Discontinued Operations, net of tax	[1]	49.1	0.4	49.1	2.8
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	[2]	$ 30.1	$ 22.7	$ 57.5	$ 43.8

[1] The impact is reflected in "Income from discontinued operations, net of tax." 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.

[2] 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 10, Retirement Benefits.