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Selling and administrative

194.2

23.0

Research and development

5.1

Other income (expense), net

(0.6)

Operating Income (Loss)

31.9

Equity affiliates’ income

0.3

Income (Loss) Before Taxes

32.2

Income tax benefit

^[1]

(53.9)

Income (Loss) From Operations of Discontinued Operations, net of tax

86.1

Gain (Loss) on Disposal, net of tax

1,785.4

Income (Loss) from Discontinued Operations, net of tax

$ 43.2

$ (2.3)

42.2

1,871.5

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

Selling and administrative

182.3

22.5

Research and development

5.1

Other income (expense), net

0.3

Operating Income (Loss)

45.2

Equity affiliates’ income

0.3

Income (Loss) Before Taxes

45.5

Income tax benefit

^[1]

(50.8)

Income (Loss) From Operations of Discontinued Operations, net of tax

96.3

Gain (Loss) on Disposal, net of tax

$ 1,833.0

1,832.5

Income (Loss) from Discontinued Operations, net of tax

1,928.8

Valuation allowance adjustment effect on income tax provision

$ 66.0

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

Selling and administrative

11.9

0.5

Research and development

0.0

Other income (expense), net

(0.9)

Operating Income (Loss)

(13.3)

Equity affiliates’ income

0.0

Income (Loss) Before Taxes

(13.3)

Income tax benefit

(3.1)

Income (Loss) From Operations of Discontinued Operations, net of tax

(10.2)

Gain (Loss) on Disposal, net of tax

(47.1)

Income (Loss) from Discontinued Operations, net of tax

$ (1.0)

$ (57.3)

[1]	As a result of the expected gain on the 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.

Materials Technologies Separation (Narrative) (Details) $ in Millions		3 Months Ended		9 Months Ended
	Oct. 01, 2016	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Sep. 30, 2017 USD ($)
Restructuring Cost and Reserve [Line Items]
Income (loss) from discontinued operations, net of tax		$ 43.2	$ (2.3)	$ 42.2	$ 1,871.5
Business separation costs, legal and advisory fees, before tax		0.0	0.0	0.0	32.5
Materials Technologies
Restructuring Cost and Reserve [Line Items]
Net business separation costs					30.2
Tax benefit related to changes in tax positions on business separation activities			8.2		5.5
Materials Technologies \| Business separation costs
Restructuring Cost and Reserve [Line Items]
Business separation costs, legal and advisory fees, before tax					32.5
Materials Technologies \| Other non-operating income (expense), net
Restructuring Cost and Reserve [Line Items]
Pension settlement benefit					2.3
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff \| Electronic Materials Division (EMD)
Restructuring Cost and Reserve [Line Items]
Distribution ratio of common stock in spin-off	0.5
Discontinued Operations \| Electronic Materials Division (EMD)
Restructuring Cost and Reserve [Line Items]
Income (loss) from discontinued operations, net of tax		0.0	$ 0.0	0.0	$ 0.0
Assets of discontinued operations		0.0		0.0		$ 0.0
Liabilities of discontinued operations		$ 0.0		$ 0.0		$ 0.0

Cost Reduction and Asset Actions (Narrative) (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
Restructuring and Related Cost [Abstract]
Cost reduction and asset actions	$ 0.0	$ 42.7	$ 0.0	$ 103.0	$ 151.4
Cost Reduction Actions
Restructuring and Related Cost [Abstract]
Cost reduction and asset actions		42.7			154.8
Cost Reduction Actions \| Industrial Gases - Americas
Restructuring and Related Cost [Abstract]
Cost reduction and asset actions					39.3
Cost Reduction Actions \| Industrial Gases - EMEA
Restructuring and Related Cost [Abstract]
Cost reduction and asset actions					77.9
Cost Reduction Actions \| Industrial Gases - Asia
Restructuring and Related Cost [Abstract]
Cost reduction and asset actions					0.9
Cost Reduction Actions \| Industrial Gases - Global
Restructuring and Related Cost [Abstract]
Cost reduction and asset actions					2.5
Cost Reduction Actions \| Corporate and other
Restructuring and Related Cost [Abstract]
Cost reduction and asset actions					34.2
Cost Reduction Actions \| Severance And Other Benefits
Restructuring and Related Cost [Abstract]
Cost reduction and asset actions		9.5		27.5	66.3
Cost Reduction Actions \| Asset Actions/Other
Restructuring and Related Cost [Abstract]
Cost reduction and asset actions		$ 33.2		$ 78.9	88.5
Business Realignment and Reorganization
Restructuring and Related Cost [Abstract]
Favorable restructuring reserve settlement					$ 3.4

Cost Reduction and Asset Actions (Carrying Amount of Accrual) (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	Sep. 30, 2016
Restructuring Cost and Reserve [Line Items]
Cost reduction and asset actions	$ 0.0	$ 42.7	$ 0.0	$ 103.0	$ 151.4
Cost Reduction Actions
Restructuring Cost and Reserve [Line Items]
Cost reduction and asset actions		42.7			154.8
Noncash expenses					(84.2)
Cash expenditures			(25.0)		(36.9)
Amount reflected in pension liability			(0.4)		(2.0)
Amount reflected in other noncurrent liabilities					(2.2)
Currency translation adjustment					(0.3)
Accrued balance	16.1		16.1		41.5	$ 12.3
Cost Reduction Actions \| Severance And Other Benefits
Restructuring Cost and Reserve [Line Items]
Cost reduction and asset actions		9.5		27.5	66.3
Noncash expenses					0.0
Cash expenditures			(24.8)		(35.7)
Amount reflected in pension liability			(0.4)		(2.0)
Amount reflected in other noncurrent liabilities					0.0
Currency translation adjustment					(0.3)
Accrued balance	15.4		15.4		40.6	12.3
Cost Reduction Actions \| Asset Actions/Other
Restructuring Cost and Reserve [Line Items]
Cost reduction and asset actions		$ 33.2		$ 78.9	88.5
Noncash expenses					(84.2)
Cash expenditures			(0.2)		(1.2)
Amount reflected in pension liability			0.0		0.0
Amount reflected in other noncurrent liabilities					(2.2)
Currency translation adjustment					0.0
Accrued balance	$ 0.7		$ 0.7		$ 0.9	$ 0.0

Acquisitions (Narrative) (Details) $ in Millions, ¥ in Billions			3 Months Ended	9 Months Ended
	Apr. 26, 2018 USD ($)	Apr. 26, 2018 CNY (¥)	Jun. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 CNY (¥)	Sep. 30, 2017 USD ($)
Property, Plant and Equipment [Line Items]
Plant and equipment, net			$ 9,902.0	$ 9,902.0			$ 8,440.2
Additions to plant and equipment				1,158.1	$ 806.8
Equity issued related to asset acquisition			227.4	227.4
Long-term debt – related party			398.7	398.7		¥ 2.6	$ 0.0
Liability for expected cash payments to or on behalf of related party			$ 345.0	345.0		¥ 2.3
Business Acquisition [Line Items]
Business combinations, goodwill acquired during period				$ 81.4
Loan \| Lu'An Loan To Joint Venture
Property, Plant and Equipment [Line Items]
Fixed interest rate (percent)			5.50%	5.50%		5.50%
Joint Venture \| Air Products Lu'an Changzhi Co Ltd
Property, Plant and Equipment [Line Items]
Consideration transferred in asset acquisition	$ 1,200.0	¥ 7.9
Joint Venture \| Air Products Lu'an Changzhi Co Ltd
Property, Plant and Equipment [Line Items]
Ownership interest by Air Products (percent)	60.00%
Ownership interest by noncontrolling owners (percent)	40.00%
Contribution of equipment to joint venture	$ 300.0
Plant and equipment, net	1,500.0
Additions to plant and equipment	235.0	1.5
Equity issued related to asset acquisition	$ 227.0	¥ 1.4
2018 Business Combinations
Business Acquisition [Line Items]
Number of business combinations completed				8
Business combinations, aggregate purchase price, net of cash acquired				$ 355.4
Business combinations, plant and equipment acquired during the period			$ 178.4	178.4
Business combinations, goodwill acquired during period				81.4
Business combinations, tax deductible goodwill			18.0	18.0
Business combinations, recognized identifiable intangible assets			$ 105.8	$ 105.8
Acquired finite-lived intangible assets, weighted-average useful life				12 years

Inventories (Schedule of Inventory) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Sep. 30, 2017
Inventory Disclosure [Abstract]
Finished goods	$ 126.7	$ 120.0
Work in process	18.5	15.7
Raw materials, supplies and other	201.0	223.0
Total FIFO cost	346.2	358.7
Less: Excess of FIFO cost over LIFO cost	(24.1)	(23.3)
Inventories	$ 322.1	$ 335.4

Equity Affiliates (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Schedule of Equity Method Investments [Line Items]
Impact of new tax law on equity affiliate expense		$ 32.5
Equity method investment impairment charge		$ 0.0	$ 79.5
Abdullah Hashim Industrial Gas & Equipment Co. Ltd
Schedule of Equity Method Investments [Line Items]
Ownership percentage of equity affiliate	25.00%		25.00%
Equity method investment impairment charge	$ 79.5

Goodwill (Schedule of Goodwill by Segment) (Details) $ in Millions	9 Months Ended
	Jun. 30, 2018 USD ($)
Goodwill [Roll Forward]
Goodwill, net, beginning balance	$ 721.5
Acquisitions	81.4
Currency translation	(8.8)
Goodwill, net, ending balance	794.1
Industrial Gases - Americas
Goodwill [Roll Forward]
Goodwill, net, beginning balance	163.7
Acquisitions	0.0
Currency translation	(1.4)
Goodwill, net, ending balance	162.3
Industrial Gases - EMEA
Goodwill [Roll Forward]
Goodwill, net, beginning balance	402.4
Acquisitions	30.8
Currency translation	(7.7)
Goodwill, net, ending balance	425.5
Industrial Gases - Asia
Goodwill [Roll Forward]
Goodwill, net, beginning balance	135.2
Acquisitions	39.8
Currency translation	0.3
Goodwill, net, ending balance	175.3
Industrial Gases - Global
Goodwill [Roll Forward]
Goodwill, net, beginning balance	20.2
Acquisitions	0.0
Currency translation	0.0
Goodwill, net, ending balance	20.2
Corporate and other
Goodwill [Roll Forward]
Goodwill, net, beginning balance	0.0
Acquisitions	10.8
Currency translation	0.0
Goodwill, net, ending balance	$ 10.8

Goodwill (Schedule of Accumulated Impairment Losses) (Details) - USD ($)
$ in Millions

Jun. 30, 2018

Sep. 30, 2017

Goodwill [Line Items]

Goodwill, gross

$ 1,201.8

$ 1,138.7

Goodwill, net

794.1

721.5

Industrial Gases - Americas

Goodwill [Line Items]

Goodwill, accumulated impairment losses

^[1]

(407.7)

(417.2)

Goodwill, net

$ 162.3

$ 163.7

[1]	Accumulated impairment losses are attributable to our Latin America reporting unit (LASA) within the Industrial Gases – Americas segment and include impairment charges recorded in previous years as well as the impacts of currency translation on the losses.

Goodwill (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Goodwill (Narrative) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Jun. 30, 2017
Industrial Gases - Americas
Goodwill [Line Items]
Goodwill impairment charge	$ 145.3	$ 145.3

Intangible Assets (Acquired Intangible Assets) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Sep. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible assets, gross	$ 665.9	$ 578.7
Accumulated amortization and impairment	(216.9)	(210.4)
Intangible assets, net	449.0	368.3
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	603.2	510.9
Accumulated amortization	(203.3)	(189.5)
Finite-lived intangible assets, net	399.9	321.4
Trade names and trademarks
Acquired Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived intangible assets, gross	62.7	67.8
Accumulated impairment	(13.6)	(20.9)
Indefinite-lived intangible assets, net	49.1	46.9
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	497.6	424.1
Accumulated amortization	(158.2)	(142.3)
Finite-lived intangible assets, net	339.4	281.8
Patents and technology
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	34.1	13.4
Accumulated amortization	(11.3)	(10.6)
Finite-lived intangible assets, net	22.8	2.8
Other
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	71.5	73.4
Accumulated amortization	(33.8)	(36.6)
Finite-lived intangible assets, net	$ 37.7	$ 36.8

Intangible Assets (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Jun. 30, 2017	Jun. 30, 2017
Industrial Gases - Americas
Schedule of Intangible Assets [Line Items]
Impairment charge	$ 16.8	$ 16.8

Financial Instruments (Narrative) (Details) € in Millions	9 Months Ended		12 Months Ended
Financial Instruments (Narrative) (Details) € in Millions	Jun. 30, 2018 USD ($)	Jun. 30, 2018 EUR (€)	Sep. 30, 2017 USD ($)	Sep. 30, 2017 EUR (€)
Derivative [Line Items]
Net liability position of derivatives with credit risk-related contingent features	$ 51,100,000		$ 34,600,000
Collateral posted on liability positions with credit risk-related contingent features	0
Collateral amount that counterparties would be required to post	$ 109,900,000		138,500,000
Forward Exchange Contracts \| Cash Flow Hedges
Derivative [Line Items]
Maximum remaining maturity of foreign currency derivatives	1 year 9 months 18 days	1 year 9 months 18 days
Foreign Currency Debt \| Euro Denominated
Derivative [Line Items]
Notional amount included in designated foreign currency denominated debt	$ 1,063,300,000	€ 910.1	$ 1,077,700,000	€ 912.2

Financial Instruments (Schedule of Outstanding Currency Price Risk Management Instruments) (Details) - Forward Exchange Contracts - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Jun. 30, 2018	Sep. 30, 2017
Derivative [Line Items]
US$ Notional	$ 4,385.8	$ 4,099.5
Years Average Maturity	10 months	10 months
Designated as Hedging Instrument \| Cash Flow Hedges
Derivative [Line Items]
US$ Notional	$ 2,905.0	$ 3,150.2
Years Average Maturity	5 months	5 months
Designated as Hedging Instrument \| Net Investment Hedges
Derivative [Line Items]
US$ Notional	$ 359.8	$ 675.5
Years Average Maturity	2 years 2 months	3 years
Not Designated as Hedging Instrument
Derivative [Line Items]
US$ Notional	$ 1,121.0	$ 273.8
Years Average Maturity	1 year 5 months	1 month

Financial Instruments (Schedule of Interest Rate Swaps and Cross Currency Interest Rate Swaps) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Jun. 30, 2018	Sep. 30, 2017
Interest Rate Swaps Contracts \| Designated as Hedging Instrument \| Fair Value Hedges
Derivative [Line Items]
US$ Notional	$ 600.0	$ 600.0
Average Pay %	LIBOR	LIBOR
Average Receive %	2.60%	2.28%
Years Average Maturity	1 year 10 months 24 days	1 year 3 months 18 days
Cross Currency Interest Rate Swaps \| Designated as Hedging Instrument \| Net Investment Hedges
Derivative [Line Items]
US$ Notional	$ 692.6	$ 539.7
Average Pay %	3.72%	3.27%
Average Receive %	2.76%	2.59%
Years Average Maturity	2 years 1 month 6 days	1 year 10 months 24 days
Cross Currency Interest Rate Swaps \| Designated as Hedging Instrument \| Cash Flow Hedges
Derivative [Line Items]
US$ Notional	$ 916.6	$ 1,095.7
Average Pay %	5.33%	4.96%
Average Receive %	2.73%	2.78%
Years Average Maturity	2 years 3 months 18 days	2 years 4 months 24 days
Cross Currency Interest Rate Swaps \| Not Designated as Hedging Instrument
Derivative [Line Items]
US$ Notional	$ 35.6	$ 41.6
Average Pay %	3.16%	3.28%
Average Receive %	2.86%	2.32%
Years Average Maturity	1 year 2 months 12 days	1 year 8 months 12 days

Financial Instruments (Fair Value of Derivative Instruments) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Sep. 30, 2017
Derivative [Line Items]
Total Derivatives, Assets	$ 157.1	$ 227.8
Total Derivatives, Liabilities	106.3	131.9
Designated as Hedging Instrument
Derivative [Line Items]
Total Derivatives, Assets	132.3	222.5
Total Derivatives, Liabilities	79.1	128.7
Designated as Hedging Instrument \| Other Receivables \| Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Assets	25.1	81.7
Designated as Hedging Instrument \| Other Receivables \| Interest Rate Management Contracts
Derivative [Line Items]
Total Derivatives, Assets	16.0	11.1
Designated as Hedging Instrument \| Other Noncurrent Assets \| Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Assets	17.4	27.1
Designated as Hedging Instrument \| Other Noncurrent Assets \| Interest Rate Management Contracts
Derivative [Line Items]
Total Derivatives, Assets	73.8	102.6
Designated as Hedging Instrument \| Accrued Liabilities \| Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Liabilities	47.4	82.0
Designated as Hedging Instrument \| Accrued Liabilities \| Interest Rate Management Contracts
Derivative [Line Items]
Total Derivatives, Liabilities	5.5	10.7
Designated as Hedging Instrument \| Other Noncurrent Liabilities \| Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Liabilities	5.6	13.8
Designated as Hedging Instrument \| Other Noncurrent Liabilities \| Interest Rate Management Contracts
Derivative [Line Items]
Total Derivatives, Liabilities	20.6	22.2
Not Designated as Hedging Instrument
Derivative [Line Items]
Total Derivatives, Assets	24.8	5.3
Total Derivatives, Liabilities	27.2	3.2
Not Designated as Hedging Instrument \| Other Receivables \| Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Assets	5.6	1.1
Not Designated as Hedging Instrument \| Other Receivables \| Interest Rate Management Contracts
Derivative [Line Items]
Total Derivatives, Assets	0.0	0.0
Not Designated as Hedging Instrument \| Other Noncurrent Assets \| Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Assets	14.2	0.0
Not Designated as Hedging Instrument \| Other Noncurrent Assets \| Interest Rate Management Contracts
Derivative [Line Items]
Total Derivatives, Assets	5.0	4.2
Not Designated as Hedging Instrument \| Accrued Liabilities \| Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Liabilities	5.3	2.2
Not Designated as Hedging Instrument \| Accrued Liabilities \| Interest Rate Management Contracts
Derivative [Line Items]
Total Derivatives, Liabilities	0.1	1.0
Not Designated as Hedging Instrument \| Other Noncurrent Liabilities \| Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Liabilities	21.8	0.0
Not Designated as Hedging Instrument \| Other Noncurrent Liabilities \| Interest Rate Management Contracts
Derivative [Line Items]
Total Derivatives, Liabilities	$ 0.0	$ 0.0

Financial Instruments (Schedule of Gain/Loss Related to Derivative Instruments) (Details) - USD ($)
$ in Millions

3 Months Ended

9 Months Ended

Jun. 30, 2018

Jun. 30, 2017

Jun. 30, 2018

Jun. 30, 2017

Designated as Hedging Instrument | Cash Flow Hedges

Net gain (loss) recognized in OCI (effective portion)

$ 27.1

$ 23.0

$ 35.4

$ (2.2)

Net (gain) loss reclassified from OCI to sales/cost of sales (effective portion)

1.9

4.3

6.9

10.1

Net (gain) loss reclassified from OCI to other income (expense), net (effective portion)

(21.9)

(27.2)

(36.6)

(0.9)

Net (gain) loss reclassified from OCI to interest expense (effective portion)

2.8

1.1

6.3

0.1

Net (gain) loss reclassified from OCI to other income (expense), net (ineffective portion)

(0.5)

(1.8)

(1.0)

(1.5)

Designated as Hedging Instrument | Fair Value Hedges

Net gain (loss) recognized in interest expense

^[1]

(2.1)

(0.6)

(8.9)

(12.5)

Designated as Hedging Instrument | Net Investment Hedges

Not Designated as Hedging Instrument

97.3

(77.4)

0.6

(9.7)

Net gain (loss) recognized in other income (expense), net

^[2]

1.9

3.0

(1.5)

2.8

Forward Exchange Contracts | Designated as Hedging Instrument | Cash Flow Hedges

Net gain (loss) recognized in OCI (effective portion)

(34.4)

41.2

5.0

(7.1)

Net (gain) loss reclassified from OCI to sales/cost of sales (effective portion)

1.9

4.3

6.9

10.1

Net (gain) loss reclassified from OCI to other income (expense), net (effective portion)

33.7

(37.9)

(13.2)

0.8

Net (gain) loss reclassified from OCI to interest expense (effective portion)

0.8

0.4

3.0

(2.0)

Net (gain) loss reclassified from OCI to other income (expense), net (ineffective portion)

0.0

(1.8)

(0.5)

(1.5)

Forward Exchange Contracts | Designated as Hedging Instrument | Net Investment Hedges

Forward Exchange Contracts | Not Designated as Hedging Instrument

16.2

(23.2)

(6.5)

3.9

Net gain (loss) recognized in other income (expense), net

^[2]

(0.3)

3.7

(0.2)

3.3

Foreign Currency Debt | Designated as Hedging Instrument | Net Investment Hedges

Other Contracts | Designated as Hedging Instrument | Cash Flow Hedges

44.2

(44.4)

4.7

(10.4)

Net gain (loss) recognized in OCI (effective portion)

^[3]

61.5

(18.2)

30.4

4.9

Net (gain) loss reclassified from OCI to sales/cost of sales (effective portion)

^[3]

0.0

Net (gain) loss reclassified from OCI to other income (expense), net (effective portion)

^[3]

(55.6)

10.7

(23.4)

(1.7)

Net (gain) loss reclassified from OCI to interest expense (effective portion)

^[3]

2.0

0.7

3.3

2.1

Net (gain) loss reclassified from OCI to other income (expense), net (ineffective portion)

^[3]

(0.5)

0.0

(0.5)

0.0

Other Contracts | Designated as Hedging Instrument | Fair Value Hedges

Net gain (loss) recognized in interest expense

^[1],[3]

(2.1)

(0.6)

(8.9)

(12.5)

Other Contracts | Designated as Hedging Instrument | Net Investment Hedges

Other Contracts | Not Designated as Hedging Instrument

^[3]

36.9

(9.8)

2.4

(3.2)

Net gain (loss) recognized in other income (expense), net

^[2],[3]

$ 2.2

$ (0.7)

$ (1.3)

$ (0.5)

[1]	The impact of fair value hedges noted above was largely offset by recognized gains and losses resulting from the impact of changes in related interest rates on outstanding debt.
[2]	The impact of the non-designated hedges noted above was largely offset by recognized gains and losses resulting from the impact of changes in exchange rates on assets and liabilities denominated in non-functional currencies.
[3]	Other includes the impact on other comprehensive income (OCI) and earnings primarily related to interest rate and cross currency interest rate swaps.

Fair Value Measurements (Schedule of the Carrying Values and Fair Values of Financial Instruments) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Sep. 30, 2017
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, including current portion, carrying value	$ 3,780.8	$ 3,818.8
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, including current portion fair value	3,822.3	3,928.2
Forward Exchange Contracts \| Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	62.3	109.9
Derivative liabilities	80.1	98.0
Forward Exchange Contracts \| Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	62.3	109.9
Derivative liabilities	80.1	98.0
Interest Rate Management Contracts \| Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	94.8	117.9
Derivative liabilities	26.2	33.9
Interest Rate Management Contracts \| Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	94.8	117.9
Derivative liabilities	$ 26.2	$ 33.9

Fair Value Measurements (Schedule of Recurring Fair Value Measurements) (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Millions	Jun. 30, 2018	Sep. 30, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Assets at Fair Value	$ 157.1	$ 227.8
Total Liabilities at Fair Value	106.3	131.9
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Assets at Fair Value	0.0	0.0
Total Liabilities at Fair Value	0.0	0.0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Assets at Fair Value	157.1	227.8
Total Liabilities at Fair Value	106.3	131.9
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Assets at Fair Value	0.0	0.0
Total Liabilities at Fair Value	0.0	0.0
Forward Exchange Contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	62.3	109.9
Derivative liabilities	80.1	98.0
Forward Exchange Contracts \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0.0	0.0
Derivative liabilities	0.0	0.0
Forward Exchange Contracts \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	62.3	109.9
Derivative liabilities	80.1	98.0
Forward Exchange Contracts \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0.0	0.0
Derivative liabilities	0.0	0.0
Interest Rate Management Contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	94.8	117.9
Derivative liabilities	26.2	33.9
Interest Rate Management Contracts \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0.0	0.0
Derivative liabilities	0.0	0.0
Interest Rate Management Contracts \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	94.8	117.9
Derivative liabilities	26.2	33.9
Interest Rate Management Contracts \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0.0	0.0
Derivative liabilities	$ 0.0	$ 0.0

Retirement Benefits (Narrative) (Details) - Defined Benefit Pension Plan - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Company contributions	$ 43.0	$ 57.0	$ 64.1
Minimum
Defined Benefit Plan Disclosure [Line Items]
Total expected contributions for current fiscal year	50.0
Maximum
Defined Benefit Plan Disclosure [Line Items]
Total expected contributions for current fiscal year	$ 70.0
Discontinued Operations
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 1.3

Retirement Benefits (Schedule of Net Periodic Benefit Cost) (Details) - Defined Benefit Pension Plan - USD ($)
$ in Millions

3 Months Ended

9 Months Ended

Jun. 30, 2018

Jun. 30, 2017

Jun. 30, 2018

Jun. 30, 2017

Discontinued Operations

Service cost

$ 1.3

U.S.

Expected return on plan assets

Service cost

$ 6.4

$ 7.0

$ 19.2

^[1]

22.2

^[1]

Interest cost

26.8

27.5

80.3

80.0

(50.4)

(51.6)

(151.2)

(156.0)

Prior service cost amortization

0.4

0.6

1.2

1.8

Actuarial loss amortization

21.8

20.9

65.7

67.9

Settlements

1.5

5.5

4.8

9.6

Curtailment

0.0

4.3

Special termination benefits

0.0

0.8

0.4

1.8

Other

0.0

U.S. | Discontinued Operations

6.5

10.7

20.4

31.6

U.S. | Continuing Operations

0.0

0.7

6.5

10.7

20.4

30.9

International

Expected return on plan assets

Service cost

6.5

19.4

^[1]

19.5

^[1]

Interest cost

9.4

8.2

28.2

23.7

(20.6)

(18.9)

(61.9)

(55.7)

Prior service cost amortization

0.0

(0.1)

Actuarial loss amortization

10.2

13.5

30.5

40.6

Settlements

0.0

1.7

Curtailment

0.0

(1.3)

Special termination benefits

0.0

0.5

Other

0.3

0.2

0.9

0.7

International | Discontinued Operations

5.8

9.5

17.1

29.6

International | Continuing Operations

0.0

4.1

Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]

$ 5.8

$ 9.5

$ 17.1

$ 25.5

[1]	Includes total service costs from discontinued operations of $1.3 for the nine months ended 30 June 2017.

Commitments and Contingencies (Litigation and Environmental - Narrative) (Details) R$ in Millions	1 Months Ended	9 Months Ended
	Sep. 30, 2010 BRL (R$)	Jun. 30, 2018 USD ($) site	Jun. 30, 2018 BRL (R$) site	Sep. 30, 2017 USD ($)
Alleged Anticompete Litigation
Loss Contingencies [Line Items]
Civil fines imposed	R$ 179.2	$ 46,000,000
Provision for litigation		0
Maximum of loss contingency range subject to interest		$ 46,000,000	R$ 179.2
Environmental
Loss Contingencies [Line Items]
Approximate number of sites on which settlement has not been reached \| site		34	34
Accrual for environmental loss contingencies		$ 78,400,000		$ 83,600,000
Accrual for environmental loss contingencies, maximum payout period		30 years
Environmental \| Minimum
Loss Contingencies [Line Items]
Estimate of possible exposure from environmental loss contingencies		$ 78,000,000
Environmental \| Maximum
Loss Contingencies [Line Items]
Estimate of possible exposure from environmental loss contingencies		$ 92,000,000

Commitments and Contingencies (Pace, Piedmont, Pasadena Narrative) (Details) - USD ($)	9 Months Ended	12 Months Ended
	Jun. 30, 2018	Sep. 30, 2012	Sep. 30, 2008	Sep. 30, 2006
Pace, Florida
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	$ 26,700,000			$ 42,000,000
Change in estimated exposure	0
Pace, Florida \| Discontinued Operations
Loss Contingencies [Line Items]
Pretax environmental expense				42,000,000
Pace, Florida \| Minimum
Loss Contingencies [Line Items]
Estimate of possible exposure from environmental loss contingencies				42,000,000
Pace, Florida \| Maximum
Loss Contingencies [Line Items]
Estimate of possible exposure from environmental loss contingencies				$ 52,000,000
Piedmont, South Carolina
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	15,900,000		$ 24,000,000
Piedmont, South Carolina \| Discontinued Operations
Loss Contingencies [Line Items]
Pretax environmental expense			$ 24,000,000
Pasadena, Texas
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	$ 11,800,000
Total anticipated exposure		$ 13,000,000

Commitments and Contingencies (Asset Retirement Obligations) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Asset retirement obligations	$ 185.8	$ 144.7

Commitments and Contingencies (Unconditional Purchase Obligations) (Details) $ in Millions	Jun. 30, 2018 USD ($)
Helium Purchases
Unrecorded Unconditional Purchase Obligation [Line Items]
Unconditional purchase obligation	$ 6,500

Share-Based Compensation (Narrative) (Details)	9 Months Ended
Share-Based Compensation (Narrative) (Details)	Jun. 30, 2018 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grant	4,656,128
Market-Based Deferred Stock Unit
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of units/shares granted	105,268
Performance period	3 years
Weighted average grant date fair value (in dollars per unit/share) \| $ / shares	$ 202.50
Time-Based Deferred Stock Unit
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of units/shares granted	141,189
Weighted average grant date fair value (in dollars per unit/share) \| $ / shares	$ 162.07

Share-Based Compensation (Compensation Cost Recognized in Income Statement) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Before-tax share-based compensation cost	$ 7.9	$ 8.9	$ 30.4	$ 27.4
Income tax benefit	(1.9)	(3.2)	(7.2)	(9.5)
After-tax share-based compensation cost	$ 6.0	$ 5.7	$ 23.2	$ 17.9

Share-Based Compensation (Market-Based Deferred Stock Unit Valuation Assumptions) (Details) - Market-Based Deferred Stock Unit	9 Months Ended
	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	18.70%
Risk-free interest rate	1.90%
Expected dividend yield	2.60%

Equity (Changes in Equity) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Stockholders' Equity [Roll Forward]
Beginning balance	$ 10,693.2	$ 9,420.2	$ 10,185.5	$ 7,213.4
Net income	487.9	104.1	1,073.2	2,546.2
Other comprehensive income (loss)	(357.0)	176.8	(40.8)	161.8
Dividends on common stock	(241.2)	(207.0)	(690.3)	(601.0)
Dividends to noncontrolling interests	(15.4)	(7.9)	(26.0)	(19.5)
Share-based compensation	7.9	8.9	29.7	27.4
Treasury shares for stock option and award plans	5.4	17.8	45.5	25.5
Spin-off of Versum			0.0	(152.6)
Cumulative change in accounting principle			0.0	8.8
Lu'An joint venture	227.4		227.4
Other equity transactions	1.8	(3.0)	5.8	(5.3)
Ending balance	$ 10,810.0	$ 9,509.9	$ 10,810.0	$ 9,509.9
Dividends per share (in dollars per share)	$ 1.10	$ 0.95	$ 3.15	$ 2.76
Air Products Shareholders' Equity
Stockholders' Equity [Roll Forward]
Beginning balance	$ 10,580.8	$ 9,317.4	$ 10,086.2	$ 7,079.6
Net income	473.9	101.9	1,044.9	2,531.7
Other comprehensive income (loss)	(342.5)	176.6	(30.4)	159.7
Dividends on common stock	(241.2)	(207.0)	(690.3)	(601.0)
Share-based compensation	7.9	8.9	29.7	27.4
Treasury shares for stock option and award plans	5.4	17.8	45.5	25.5
Spin-off of Versum			0.0	(186.5)
Cumulative change in accounting principle			0.0	8.8
Other equity transactions	1.7	(3.2)	0.4	(5.8)
Ending balance	10,486.0	9,412.4	10,486.0	9,412.4
Non-controlling Interests
Stockholders' Equity [Roll Forward]
Beginning balance	112.4	102.8	99.3	133.8
Net income	14.0	2.2	28.3	14.5
Other comprehensive income (loss)	(14.5)	0.2	(10.4)	2.1
Dividends to noncontrolling interests	(15.4)	(7.9)	(26.0)	(19.5)
Spin-off of Versum			0.0	(33.9)
Lu'An joint venture	227.4		227.4
Other equity transactions	0.1	0.2	5.4	0.5
Ending balance	$ 324.0	$ 97.5	$ 324.0	$ 97.5

Accumulated Other Comprehensive Loss (Rollforward) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 10,693.2	$ 9,420.2	$ 10,185.5	$ 7,213.4
Other comprehensive income (loss) before reclassifications	(365.3)		(95.0)
Amounts reclassified from AOCL	8.3		54.2
Total Other Comprehensive Income (Loss)	(357.0)	176.8	(40.8)	161.8
Amount attributable to noncontrolling interests	(14.5)	0.2	(10.4)	2.1
Ending balance	10,810.0	$ 9,509.9	10,810.0	$ 9,509.9
Derivatives qualifying as hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(51.4)		(53.1)
Other comprehensive income (loss) before reclassifications	27.1		35.4
Amounts reclassified from AOCL	(17.7)		(24.4)
Total Other Comprehensive Income (Loss)	9.4		11.0
Amount attributable to noncontrolling interests	0.1		0.0
Ending balance	(42.1)		(42.1)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(526.2)		(787.1)
Other comprehensive income (loss) before reclassifications	(392.4)		(130.4)
Amounts reclassified from AOCL	0.0		3.1
Total Other Comprehensive Income (Loss)	(392.4)		(127.3)
Amount attributable to noncontrolling interests	(14.6)		(10.4)
Ending balance	(904.0)		(904.0)
Pension and postretirement benefits
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(957.7)		(1,007.2)
Other comprehensive income (loss) before reclassifications	0.0		0.0
Amounts reclassified from AOCL	26.0		75.5
Total Other Comprehensive Income (Loss)	26.0		75.5
Amount attributable to noncontrolling interests	0.0		0.0
Ending balance	(931.7)		(931.7)
AOCL attributable to Air Products
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(1,535.3)		(1,847.4)
Ending balance	$ (1,877.8)		$ (1,877.8)

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

Other income/expense, net

$ (5.8)

$ (26.3)

$ (43.2)

$ (73.0)

Interest expense

34.9

29.8

95.1

89.8

Cost reduction and asset actions

1,545.4

1,486.0

4,623.7

4,206.5

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)

Reclassification out of Accumulated Other Comprehensive Income | (Gain) Loss on Cash Flow Hedges, net of tax

(473.9)

(101.9)

(1,044.9)

(2,531.7)

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

Reclassification out of Accumulated Other Comprehensive Income | Currency Translation Adjustment

(17.7)

(23.6)

(24.4)

7.8

Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]

Cost reduction and asset actions

^[1]

0.0

3.1

0.0

^[2]

0.0

8.2

0.0

8.2

Loss from discontinued operations, net of tax

^[3]

0.0

49.1

Reclassification out of Accumulated Other Comprehensive Income | Pension and Postretirement Benefits, net of tax

0.0

8.2

3.1

57.3

Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]