Business Segment and Geographic Information (Schedule of Assets Information) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Sep. 30, 2012
Segment Reporting Information [Line Items]
Identifiable Assets	$ 16,023.0	[1]	$ 15,766.1	[1]
Merchant Gases [Member]
Segment Reporting Information [Line Items]
Identifiable Assets	6,512.2	[1]	6,428.5	[1]
Tonnage Gases [Member]
Segment Reporting Information [Line Items]
Identifiable Assets	5,221.4	[1]	5,059.8	[1]
Electronics and Performance Materials [Member]
Segment Reporting Information [Line Items]
Identifiable Assets	2,874.4	[1]	2,930.3	[1]
Equipment and Energy [Member]
Segment Reporting Information [Line Items]
Identifiable Assets	472.0	[1]	379.3	[1]
Segment Total [Member]
Segment Reporting Information [Line Items]
Identifiable Assets	15,080.0	[1]	14,797.9	[1]
All Other Segments [Member]
Segment Reporting Information [Line Items]
Identifiable Assets	907.6	[1]	925.4	[1]
Discontinued Operations [Member]
Segment Reporting Information [Line Items]
Identifiable Assets	$ 35.4	[1]	$ 42.8	[1]

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