Goodwill (Schedule of Goodwill by Segment) (Details) $ in Millions	6 Months Ended
Mar. 31, 2019 USD ($)
Goodwill [Roll Forward]
Goodwill, net, beginning balance	$ 788.9
Acquisitions	38.0
Currency translation	(15.0)
Goodwill, net, ending balance	811.9
Industrial Gases - Americas
Goodwill [Roll Forward]
Goodwill, net, beginning balance	162.1
Acquisitions	0.0
Currency translation	(2.0)
Goodwill, net, ending balance	160.1
Industrial Gases - EMEA
Goodwill [Roll Forward]
Goodwill, net, beginning balance	424.4
Acquisitions	38.0
Currency translation	(13.4)
Goodwill, net, ending balance	449.0
Industrial Gases - Asia
Goodwill [Roll Forward]
Goodwill, net, beginning balance	171.9
Acquisitions	0.0
Currency translation	0.3
Goodwill, net, ending balance	172.2
Industrial Gases - Global
Goodwill [Roll Forward]
Goodwill, net, beginning balance	20.1
Acquisitions	0.0
Currency translation	(0.2)
Goodwill, net, ending balance	19.9
Corporate and other
Goodwill [Roll Forward]
Goodwill, net, beginning balance	10.4
Acquisitions	0.0
Currency translation	0.3
Goodwill, net, ending balance	$ 10.7

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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