Goodwill (Schedule of Goodwill by Segment) (Details) $ in Millions	6 Months Ended
Mar. 31, 2021 USD ($)
Goodwill [Roll Forward]
Goodwill, net, beginning balance	$ 891.5
Acquisitions	14.5
Currency translation and other	8.7
Goodwill, net, ending balance	914.7
Industrial Gases - Americas
Goodwill [Roll Forward]
Goodwill, net, beginning balance	152.6
Acquisitions	0.0
Currency translation and other	4.4
Goodwill, net, ending balance	157.0
Industrial Gases - EMEA
Goodwill [Roll Forward]
Goodwill, net, beginning balance	524.1
Acquisitions	14.5
Currency translation and other	0.9
Goodwill, net, ending balance	539.5
Industrial Gases - Asia
Goodwill [Roll Forward]
Goodwill, net, beginning balance	180.4
Acquisitions	0.0
Currency translation and other	3.0
Goodwill, net, ending balance	183.4
Business combinations, tax deductible goodwill	0.0
Industrial Gases - Global
Goodwill [Roll Forward]
Goodwill, net, beginning balance	19.5
Acquisitions	0.0
Currency translation and other	0.4
Goodwill, net, ending balance	19.9
Corporate and other
Goodwill [Roll Forward]
Goodwill, net, beginning balance	14.9
Acquisitions	0.0
Currency translation and other	0.0
Goodwill, net, ending balance	$ 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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