Discontinued Operations (Schedule of Operating Results) (Details) - USD ($) $ in Millions		3 Months Ended					6 Months Ended
		Mar. 31, 2017		Dec. 31, 2016	Mar. 31, 2016		Mar. 31, 2017		Mar. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (loss) from discontinued operations, net of tax		$ 1,825.6			$ (750.2)		$ 1,873.8		$ (665.4)
Net Income Attributable to Noncontrolling Interests of Discontinued Operations		0.0			2.0		0.0		4.1
Net Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent		1,825.6			(752.2)		1,873.8		(669.5)
Performance Materials Division [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on disposal, net of tax		1,833.0
Energy-from-Waste [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on disposal, net of tax				$ (47.1)	(846.6)
Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales					493.8		254.8		983.3
Cost of sales		6.3			309.1		191.9		611.1
Selling and administrative		2.1			40.4		22.7		78.5
Research and development					14.7		5.1		30.2
Other income (expense), net		0.3			8.3		0.2		(5.0)
Operating Income (Loss)					137.9		35.3		258.5
Equity affiliates’ income					0.2		0.3		0.6
Income (Loss) Before Taxes		(8.1)			138.1	[1]	35.6		259.1	[1]
Income tax provision		(1.2)			41.7		(52.8)	[2]	77.9
Income (Loss) From Operations of Discontinued Operations, net of tax		(6.9)			96.4		88.4		181.2
Gain (loss) on disposal, net of tax		1,832.5					1,785.4
Loss on disposal, net of tax					(846.6)				(846.6)
Income (loss) from discontinued operations, net of tax		1,825.6			(750.2)		1,873.8		(665.4)
Net Income Attributable to Noncontrolling Interests of Discontinued Operations					2.0				4.1
Net Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent					(752.2)				(669.5)
Income (Loss) from Discontinued Operations, Before Income Tax, Attributable to Parent					135.7				254.1
Discontinued Operations [Member] | Electronic Materials Division [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales					230.7				473.3
Cost of sales					127.6				254.9
Selling and administrative					20.0				38.4
Research and development					9.5				19.6
Other income (expense), net					2.8				5.0
Operating Income (Loss)					76.4				165.4
Equity affiliates’ income					0.0				0.2
Income (Loss) Before Taxes					76.4				165.6
Income tax provision					16.7				41.6
Income (Loss) From Operations of Discontinued Operations, net of tax					59.7				124.0
Loss on disposal, net of tax					0.0				0.0
Income (loss) from discontinued operations, net of tax					59.7				124.0
Net Income Attributable to Noncontrolling Interests of Discontinued Operations					2.0				4.1
Net Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent					57.7				119.9
Discontinued Operations [Member] | Performance Materials Division [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales					263.1		254.8		510.0
Cost of sales		3.3			178.3		182.3		350.9
Selling and administrative		2.1			19.5		22.5		38.5
Research and development					4.9		5.1		9.9
Other income (expense), net		0.7			4.9		0.3		3.7
Operating Income (Loss)					65.3		45.2		114.4
Equity affiliates’ income					0.2		0.3		0.4
Income (Loss) Before Taxes		(4.7)			65.5		45.5		114.8
Income tax provision		(0.3)			22.3		(50.8)	[2]	36.9
Income (Loss) From Operations of Discontinued Operations, net of tax		(4.4)			43.2		96.3		77.9
Gain (loss) on disposal, net of tax	[3]	1,832.5					1,832.5
Loss on disposal, net of tax					0.0				0.0
Income (loss) from discontinued operations, net of tax		1,828.1			43.2		1,928.8		77.9
Net Income Attributable to Noncontrolling Interests of Discontinued Operations					0.0				0.0
Net Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent					43.2				77.9
Discontinued Operations, Allowance Adjustment Effect on Income Tax Provision				$ 66.0
Gross expense related to income tax reserves for uncertain tax positions included in gain		26.1					26.1
Net expense related to income tax reserves for uncertain tax positions included in gain		19.1					19.1
Discontinued Operations [Member] | Energy-from-Waste [Member]
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		3.0			3.2		9.6		5.3
Selling and administrative		0.0			0.9		0.2		1.6
Research and development					0.3		0.0		0.7
Other income (expense), net		(0.4)			0.6		(0.1)		(13.7)
Operating Income (Loss)					(3.8)	[4]	(9.9)	[5]	(21.3)	[4]
Equity affiliates’ income					0.0		0.0		0.0
Income (Loss) Before Taxes		(3.4)	[5]		(3.8)	[4]	(9.9)	[5]	(21.3)	[4]
Income tax provision		(0.9)			2.7		(2.0)		(0.6)
Income (Loss) From Operations of Discontinued Operations, net of tax		(2.5)	[5]		(6.5)	[4]	(7.9)	[5]	(20.7)	[4]
Gain (loss) on disposal, net of tax		0.0					(47.1)
Loss on disposal, net of tax					(846.6)				(846.6)
Income (loss) from discontinued operations, net of tax		$ (2.5)			(853.1)	[4]	$ (55.0)		(867.3)	[4]
Net Income Attributable to Noncontrolling Interests of Discontinued Operations					0.0				0.0
Net Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	[4]				$ (853.1)				$ (867.3)

[1] For the three and six months ended 31 March 2016, income before taxes from operations of discontinued operations attributable to Air Products was $135.7 and $254.1, respectively.

[2] As a result of the expected gain on sale of PMD, we released valuation allowances related to capital loss and net operating loss carryforwards during the first quarter of 2017 that favorably impacted our income tax provision within discontinued operations by approximately $66.

[3] After-tax gain on sale of $1,832.5 includes expense for income tax reserves for uncertain tax positions of $26.1 gross ($19.1 net) in various jurisdictions.

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

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