Discontinued Operations (Schedule of Operating Results) (Details) - USD ($) $ in Millions		3 Months Ended									12 Months Ended
	Jan. 03, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	[1]	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017		Sep. 30, 2016		Sep. 30, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (loss) from Discontinued Operations, net of tax											$ 1,866.0		$ (460.5)		$ 351.7
Net Income Attributable to Noncontrolling Interests of Discontinued Operations											0.0		7.9		7.1
Net Income (Loss) From Discontinued Operations		$ (5.5)	$ (2.3)	$ 1,825.6		$ 48.2	$ 104.6	$ 96.5	$ (752.2)	$ 82.7	1,866.0	[1]	(468.4)		344.6
Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales											254.8		2,020.7		2,070.6
Cost of sales											196.1		1,250.7		1,345.9
Selling and administrative											23.2		167.1		168.7
Research and development											5.1		61.3		62.4
Other income (expense), net											(1.7)		(6.3)		(27.7)	[2]
Operating Income (Loss)											28.7		535.3		465.9
Equity affiliates' income											0.3		1.6		2.2
Interest expense													0.3		0.7
Income (Loss) Before Taxes											29.0		536.6	[3]	467.4	[4]
Income tax provision (benefit)											(56.5)	[5]	150.5		115.7
Income (Loss) From Operations of Discontinued Operations, net of tax											85.5		386.1
Gain (Loss) on Disposal, net of tax											1,780.5
Loss on Disposal, net of tax													(846.6)
Income (loss) from Discontinued Operations, net of tax											1,866.0		(460.5)		351.7
Net Income Attributable to Noncontrolling Interests of Discontinued Operations													7.9		7.1
Net Income (Loss) From Discontinued Operations													(468.4)		344.6
Income before taxes from operations of discontinued operations attributable to Air Products													527.1		458.9
Electronic Materials Division (EMD) | Discontinued Operations, Spinoff
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales													961.6		984.1
Cost of sales													521.6		586.8
Selling and administrative													87.7		86.4
Research and development													40.8		37.5
Other income (expense), net													2.2		(18.5)	[2]
Operating Income (Loss)													313.7		254.9
Equity affiliates' income													0.2		1.0
Interest expense													0.3		0.1
Income (Loss) Before Taxes													313.6		255.8
Income tax provision (benefit)													73.4		49.7
Income (Loss) From Operations of Discontinued Operations, net of tax													240.2
Loss on Disposal, net of tax													0.0
Income (loss) from Discontinued Operations, net of tax													240.2		206.1
Net Income Attributable to Noncontrolling Interests of Discontinued Operations													7.9		7.1
Net Income (Loss) From Discontinued Operations													232.3		199.0
Performance Materials Division (PMD) | Discontinued Operations, Held-for-sale or Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales											254.8		1,059.1		1,086.5
Cost of sales											182.3		704.5		754.0
Selling and administrative											22.5		76.6		79.9
Research and development											5.1		19.6		23.2
Other income (expense), net											0.3		4.2		(9.2)	[2]
Operating Income (Loss)											45.2		262.6		220.2
Equity affiliates' income											0.3		1.4		1.2
Interest expense													0.0		0.6
Income (Loss) Before Taxes											45.5		264.0		220.8
Income tax provision (benefit)											(50.8)	[5]	80.5		68.4
Income (Loss) From Operations of Discontinued Operations, net of tax											96.3		183.5
Gain (Loss) on Disposal, net of tax	$ 1,828.0										1,827.6	[6]
Loss on Disposal, net of tax													0.0
Income (loss) from Discontinued Operations, net of tax											1,923.9		183.5		152.4
Net Income Attributable to Noncontrolling Interests of Discontinued Operations													0.0		0.0
Net Income (Loss) From Discontinued Operations													183.5		152.4
Valuation allowance adjustment effect on income tax provision						69.0
Gross expense for income tax reserves included in provision for gain on disposal											28.0
Net expense for income tax reserves included in provision for gain on disposal											21.0
Energy-from-Waste (EfW) | Discontinued Operations, Held-for-sale or Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales											0.0		0.0		0.0
Cost of sales											13.8		24.6		5.1
Selling and administrative											0.7		2.8		2.4
Research and development											0.0		0.9		1.7
Other income (expense), net											(2.0)		(12.7)		0.0	[2]
Operating Income (Loss)											(16.5)	[7]	(41.0)	[8]	(9.2)	[9]
Equity affiliates' income											0.0		0.0		0.0
Interest expense													0.0		0.0
Income (Loss) Before Taxes											(16.5)	[7]	(41.0)	[8]	(9.2)	[9]
Income tax provision (benefit)											(5.7)		(3.4)		(2.4)
Income (Loss) From Operations of Discontinued Operations, net of tax											(10.8)	[7]	(37.6)	[8]
Gain (Loss) on Disposal, net of tax											(47.1)
Loss on Disposal, net of tax						$ (47.1)			$ (846.6)				(846.6)
Income (loss) from Discontinued Operations, net of tax											$ (57.9)		(884.2)		(6.8)	[9]
Net Income Attributable to Noncontrolling Interests of Discontinued Operations													0.0		0.0
Net Income (Loss) From Discontinued Operations													$ (884.2)		$ (6.8)

[1] Includes the after-tax gain on the sale of PMD. For additional information, see Note 3, Discontinued Operations.

[2] Primarily includes business restructuring and cost reduction actions.

[3] In fiscal year 2016, income before taxes from operations of discontinued operations attributable to Air Products was $527.1.

[4] In fiscal year 2015, income before taxes from operations of discontinued operations attributable to Air Products was $458.9.

[5] As a result of the expected gain on sale of PMD, we released valuation allowances related to capital loss and net operating loss carryforwards primarily during the first quarter of 2017 that favorably impacted our income tax provision within discontinued operations by approximately $69.

[6] After-tax gain on sale of $1,827.6 includes expense for income tax reserves for uncertain tax positions of $28.0 gross ($21.0 net) in various jurisdictions.

[7] The loss from operations of discontinued operations for EfW primarily relates to costs incurred for ongoing project exit activities, administrative costs, and land lease obligations.

[8] The loss from operations of discontinued operations for EfW primarily relates to project suspension costs, land lease obligations, and administrative costs.

[9] The loss from operations of discontinued operations for EfW primarily relates to land lease obligations and administrative costs.