Business Segment And Geographic Information (Segment Revenue From External Customers And Operating Income) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Mar. 31, 2012		Mar. 31, 2011		Mar. 31, 2012		Mar. 31, 2011
Segment Reporting Information [Line Items]
Sales to External Customers	$ 2,344.3		$ 2,403.0		$ 4,665.8		$ 4,695.5
Operating Income	287.9		393.8		641.7		725.0
Cost reduction plan	(86.8)				(86.8)
Net loss on Airgas transaction			(5.0)				(48.5)
Other	1.5	[1]	(1.3)	[1]	(7.8)	[1]	(7.7)	[1]
Merchant Gases [Member]
Segment Reporting Information [Line Items]
Sales to External Customers	883.6		914.4		1,771.3		1,803.0
Operating Income	152.5		165.1		318.8		341.4
Cost reduction plan	(77.3)				(77.3)
Tonnage Gases [Member]
Segment Reporting Information [Line Items]
Sales to External Customers	783.5		799.2		1,593.3		1,565.2
Operating Income	125.4		120.9		236.8		236.5
Cost reduction plan	(3.8)				(3.8)
Electronics And Performance Materials [Member]
Segment Reporting Information [Line Items]
Sales to External Customers	567.0		575.9		1,102.2		1,101.9
Operating Income	85.5		91.6		163.6		160.6
Cost reduction plan	(5.7)				(5.7)
Equipment And Energy [Member]
Segment Reporting Information [Line Items]
Sales to External Customers	110.2		113.5		199.0		225.4
Operating Income	9.8		22.5		17.1		42.7
Segment Total [Member]
Segment Reporting Information [Line Items]
Operating Income	$ 373.2		$ 400.1		$ 736.3		$ 781.2

[1] Includes stranded costs resulting from discontinued operations.