Goodwill (Schedule of Goodwill by Segment) (Details) $ in Millions	3 Months Ended
	Dec. 31, 2018 USD ($)
Goodwill [Roll Forward]
Goodwill, net, beginning balance	$ 788.9
Currency translation	(8.5)
Goodwill, net, ending balance	780.4
Industrial Gases - Americas
Goodwill [Roll Forward]
Goodwill, net, beginning balance	162.1
Currency translation	(3.2)
Goodwill, net, ending balance	158.9
Industrial Gases - EMEA
Goodwill [Roll Forward]
Goodwill, net, beginning balance	424.4
Currency translation	(5.2)
Goodwill, net, ending balance	419.2
Industrial Gases - Asia
Goodwill [Roll Forward]
Goodwill, net, beginning balance	171.9
Currency translation	(0.1)
Goodwill, net, ending balance	171.8
Industrial Gases - Global
Goodwill [Roll Forward]
Goodwill, net, beginning balance	20.1
Currency translation	(0.3)
Goodwill, net, ending balance	19.8
Corporate and other
Goodwill [Roll Forward]
Goodwill, net, beginning balance	10.4
Currency translation	0.3
Goodwill, net, ending balance	$ 10.7