Goodwill (Schedule of Goodwill by Segment) (Details) $ in Millions	3 Months Ended
Dec. 31, 2017 USD ($)
Goodwill [Roll Forward]
Goodwill, net, beginning balance	$ 721.5
Acquisitions	53.7
Currency translation	15.6
Goodwill, net, ending balance	790.8
Industrial Gases - Americas
Goodwill [Roll Forward]
Goodwill, net, beginning balance	163.7
Acquisitions	0.0
Currency translation	2.3
Goodwill, net, ending balance	166.0
Industrial Gases - EMEA
Goodwill [Roll Forward]
Goodwill, net, beginning balance	402.4
Acquisitions	17.3
Currency translation	10.9
Goodwill, net, ending balance	430.6
Industrial Gases - Asia
Goodwill [Roll Forward]
Goodwill, net, beginning balance	135.2
Acquisitions	36.4
Currency translation	2.5
Goodwill, net, ending balance	174.1
Industrial Gases - Global
Goodwill [Roll Forward]
Goodwill, net, beginning balance	20.2
Acquisitions	0.0
Currency translation	(0.1)
Goodwill, net, ending balance	$ 20.1

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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

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Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

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