Goodwill (Schedule of Accumulated Impairment Losses) (Details) - USD ($) $ in Millions		6 Months Ended	12 Months Ended
		Mar. 31, 2016	Sep. 30, 2015
Goodwill [Line Items]
Goodwill, gross		$ 1,405.1	$ 1,375.0
Goodwill, Accumulated impairment losses	[1]	(254.5)	(243.7)
Goodwill, net		1,150.6	1,131.3
Goodwill, Accumulated impairment losses currency translation		50.7	61.5
Industrial Gases Americas [Member]
Goodwill [Line Items]
Goodwill, net		$ 305.9	$ 297.6

[1] Amount is attributable to the Industrial Gases – Americas segment and includes currency translation of $50.7 and $61.5 as of 31 March 2016 and 30 September 2015, respectively.