Goodwill (Schedule of Accumulated Impairment Losses) (Details) - USD ($) $ in Millions		6 Months Ended	12 Months Ended
		Mar. 31, 2017	Sep. 30, 2016
Goodwill [Line Items]
Goodwill, gross		$ 1,084.7	$ 1,103.7
Goodwill, net		827.2	845.1
Industrial Gases - Americas [Member]
Goodwill [Line Items]
Goodwill, Accumulated impairment losses	[1]	(257.5)	(258.6)
Goodwill, net		308.2	309.1
Goodwill, Accumulated impairment losses currency translation		$ 47.7	$ 46.6

[1] Amount is attributable to the Industrial Gases – Americas segment and includes currency translation of $47.7 and $46.6 as of 31 March 2017 and 30 September 2016, respectively.