Goodwill (Schedule of Goodwill by Segment) (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019
Goodwill [Roll Forward]
Goodwill, net, beginning balance	$ 797.1	$ 788.9
Acquisitions	71.1	48.6
Currency translation and other	23.3	(40.4)
Goodwill, net, ending balance	891.5	797.1
Industrial Gases - Americas
Goodwill [Roll Forward]
Goodwill, net, beginning balance	156.3	162.1
Acquisitions	0.0	0.0
Currency translation and other	(3.7)	(5.8)
Goodwill, net, ending balance	152.6	156.3
Industrial Gases - EMEA
Goodwill [Roll Forward]
Goodwill, net, beginning balance	432.3	424.4
Acquisitions	66.6	38.5
Currency translation and other	25.2	(30.6)
Goodwill, net, ending balance	524.1	432.3
Industrial Gases - Asia
Goodwill [Roll Forward]
Goodwill, net, beginning balance	178.5	171.9
Acquisitions	0.0	10.1
Currency translation and other	1.9	(3.5)
Goodwill, net, ending balance	180.4	178.5
Industrial Gases - Global
Goodwill [Roll Forward]
Goodwill, net, beginning balance	19.6	20.1
Acquisitions	0.0	0.0
Currency translation and other	(0.1)	(0.5)
Goodwill, net, ending balance	19.5	19.6
Corporate and other
Goodwill [Roll Forward]
Goodwill, net, beginning balance	10.4	10.4
Acquisitions	4.5	0.0
Currency translation and other	0.0	0.0
Goodwill, net, ending balance	$ 14.9	$ 10.4

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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