Business Segment and Geographic Information (Schedule of Assets Information) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2010
Segment Reporting Information [Line Items]
Total Assets	$ 16,941.8		$ 14,290.7		$ 13,505.9
Investment in net assets of and advances to equity affiliates	1,175.7		1,011.6		912.8
Identifiable Assets	15,766.1		13,279.1		12,593.1
Expenditures for Long Lived Assets	1,521.0	[1]	1,309.3	[1]	988.7	[1]
Merchant Gases [Member]
Segment Reporting Information [Line Items]
Total Assets	7,411.9		5,380.0		5,337.2
Investment in net assets of and advances to equity affiliates	983.4		800.4		749.4
Identifiable Assets	6,428.5		4,579.6		4,587.9
Expenditures for Long Lived Assets	523.6	[1]	390.5	[1]	269.3	[1]
Tonnage Gases [Member]
Segment Reporting Information [Line Items]
Total Assets	5,192.2		4,581.8		3,958.1
Identifiable Assets	5,059.8		4,464.3		3,876.4
Expenditures for Long Lived Assets	630.7	[1]	669.9	[1]	557.2	[1]
Electronics and Performance Materials [Member]
Segment Reporting Information [Line Items]
Total Assets	2,969.6		2,560.7		2,336.1
Identifiable Assets	2,930.3		2,488.9		2,275.8
Expenditures for Long Lived Assets	280.8	[1]	196.0	[1]	139.0	[1]
Equipment and Energy [Member]
Segment Reporting Information [Line Items]
Total Assets	399.9		357.5		362.7
Identifiable Assets	379.3		335.6		341.3
Expenditures for Long Lived Assets	85.9	[1]	45.9	[1]	22.4	[1]
Segment Total [Member]
Segment Reporting Information [Line Items]
Total Assets	15,973.6		12,880.0		11,994.1
Identifiable Assets	14,797.9		11,868.4		11,081.4
Expenditures for Long Lived Assets	1,521.0	[1]	1,302.3	[1]	987.9	[1]
All Other Segments [Member]
Segment Reporting Information [Line Items]
Total Assets	925.4		878.6		1,009.4
Investment in net assets of and advances to equity affiliates	192.3		211.2		163.4
Identifiable Assets	925.4		878.6		1,009.3
Expenditures for Long Lived Assets	0	[1]	7.0	[1]	0.8	[1]
Discontinued Operations [Member]
Segment Reporting Information [Line Items]
Total Assets	42.8		532.1		502.4
Identifiable Assets	$ 42.8		$ 532.1		$ 502.4

[1] Includes plant and equipment