Goodwill (Schedule of Goodwill by Segment) (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020
Goodwill [Roll Forward]
Goodwill, net, beginning balance	$ 891.5	$ 797.1
Acquisitions	21.0	71.1
Currency translation and other	(1.0)	23.3
Goodwill, net, ending balance	911.5	891.5
Industrial Gases - Americas
Goodwill [Roll Forward]
Goodwill, net, beginning balance	152.6	156.3
Acquisitions	0.0	0.0
Currency translation and other	(1.6)	(3.7)
Goodwill, net, ending balance	151.0	152.6
Industrial Gases - EMEA
Goodwill [Roll Forward]
Goodwill, net, beginning balance	524.1	432.3
Acquisitions	21.0	66.6
Currency translation and other	(3.6)	25.2
Goodwill, net, ending balance	541.5	524.1
Business combinations, tax deductible goodwill	0.0
Industrial Gases - Asia
Goodwill [Roll Forward]
Goodwill, net, beginning balance	180.4	178.5
Acquisitions	0.0	0.0
Currency translation and other	3.9	1.9
Goodwill, net, ending balance	184.3	180.4
Industrial Gases - Global
Goodwill [Roll Forward]
Goodwill, net, beginning balance	19.5	19.6
Acquisitions	0.0	0.0
Currency translation and other	0.3	(0.1)
Goodwill, net, ending balance	19.8	19.5
Corporate and other
Goodwill [Roll Forward]
Goodwill, net, beginning balance	14.9	10.4
Acquisitions	0.0	4.5
Currency translation and other	0.0	0.0
Goodwill, net, ending balance	$ 14.9	$ 14.9

The amount of goodwill arising from a business combination that is expected to be deductible for tax purposes.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of increase (decrease) from foreign currency translation adjustments and purchase accounting adjustments of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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