Business Segment Information (Narratives) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Sales	$ 1,980.1	$ 1,777.4	$ 3,862.6	$ 3,643.7
Operating income (loss)	391.2	371.6	719.3	744.1
Industrial Gases - Global [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Sales	61.0	$ 56.6	$ 122.0	$ 111.2
Contracts Accounted for under Percentage of Completion [Member] | Industrial Gases - Global [Member]
Segment Reporting Information [Line Items]
Operating income (loss)	$ 12.0