Business Segment and Geographic Information (Schedule of Identifiable Assets Information) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012		Sep. 30, 2011
Segment Reporting Information [Line Items]
Identifiable Assets	$ 13,745.9	[1]	$ 13,279.1	[1]
Other Identifiable Assets	878.1	[1]	878.6	[1]
Merchant Gases [Member]
Segment Reporting Information [Line Items]
Identifiable Assets	4,591.9	[1]	4,579.6	[1]
Tonnage Gases [Member]
Segment Reporting Information [Line Items]
Identifiable Assets	4,969.2	[1]	4,464.3	[1]
Electronics and Performance Materials [Member]
Segment Reporting Information [Line Items]
Identifiable Assets	2,940.2	[1]	2,488.9	[1]
Equipment and Energy [Member]
Segment Reporting Information [Line Items]
Identifiable Assets	324.9	[1]	335.6	[1]
Discontinued Operations [Member]
Segment Reporting Information [Line Items]
Identifiable Assets	41.6	[1]	532.1	[1]
Segment Total [Member]
Segment Reporting Information [Line Items]
Identifiable Assets	$ 12,826.2	[1]	$ 11,868.4	[1]

[1] Identifiable assets are equal to total assets less investment in net assets of and advances to equity affiliates.