Plant and Equipment (Major Classes of Plant and Equipment) (Details) (USD $) In Millions, unless otherwise specified				12 Months Ended								12 Months Ended						12 Months Ended								12 Months Ended								12 Months Ended								12 Months Ended								12 Months Ended						12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2012 Cylinders [Member] Minimum [Member]	Sep. 30, 2012 Cylinders [Member] Maximum [Member]	Sep. 30, 2012 Tank [Member]	Sep. 30, 2012 Customer Station [Member]	Sep. 30, 2012 Tractor Trailer [Member] Minimum [Member]	Sep. 30, 2012 Tractor Trailer [Member] Maximum [Member]	Sep. 30, 2012 Land [Member]	Sep. 30, 2011 Land [Member]	Sep. 30, 2012 Building [Member]	Sep. 30, 2011 Building [Member]	Sep. 30, 2012 Production Facility [Member]		Sep. 30, 2011 Production Facility [Member]		Sep. 30, 2012 Production Facility [Member] Merchant Gases [Member]		Sep. 30, 2011 Production Facility [Member] Merchant Gases [Member]		Sep. 30, 2012 Production Facility [Member] Tonnage Gases [Member]		Sep. 30, 2011 Production Facility [Member] Tonnage Gases [Member]		Sep. 30, 2012 Production Facility [Member] Tonnage Gases [Member] Minimum [Member]		Sep. 30, 2012 Production Facility [Member] Tonnage Gases [Member] Maximum [Member]		Sep. 30, 2012 Production Facility [Member] Electronics and Performance Materials [Member]		Sep. 30, 2011 Production Facility [Member] Electronics and Performance Materials [Member]		Sep. 30, 2012 Production Facility [Member] Electronics and Performance Materials [Member] Minimum [Member]		Sep. 30, 2012 Production Facility [Member] Electronics and Performance Materials [Member] Maximum [Member]		Sep. 30, 2012 Production Facility [Member] Equipment and Energy [Member]		Sep. 30, 2011 Production Facility [Member] Equipment and Energy [Member]		Sep. 30, 2012 Production Facility [Member] Equipment and Energy [Member] Minimum [Member]		Sep. 30, 2012 Production Facility [Member] Equipment and Energy [Member] Maximum [Member]		Sep. 30, 2012 Distribution equipment		Sep. 30, 2011 Distribution equipment		Sep. 30, 2012 Distribution equipment Minimum [Member]		Sep. 30, 2012 Distribution equipment Maximum [Member]		Sep. 30, 2012 Other Machinery and Equipment [Member]	Sep. 30, 2011 Other Machinery and Equipment [Member]	Sep. 30, 2012 Other Machinery and Equipment [Member] Minimum [Member]	Sep. 30, 2012 Other Machinery and Equipment [Member] Maximum [Member]	Sep. 30, 2012 Construction in Progress [Member]	Sep. 30, 2011 Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Plant and Equipment, at cost	$ 18,046.2	$ 16,858.8								$ 215.8	$ 173.1	$ 1,032.8	$ 913.8	$ 12,333.1	[1]	$ 11,543.9	[1]	$ 3,552.9	[1]	$ 3,249.2	[1]	$ 6,583.7	[1]	$ 6,266.5	[1]					$ 2,022.6	[1]	$ 1,862.3	[1]					$ 173.9	[1]	$ 165.9	[1]					$ 3,133.7	[2]	$ 2,770.7	[2]					$ 310.7	$ 221.2			$ 1,020.1	$ 1,236.1
Less: accumulated depreciation	9,805.6	9,636.1
Plant and equipment, net	$ 8,240.6	$ 7,222.7	$ 6,849.3
Average useful life				10 years	25 years	20 years	7 years 6 months	5 years	15 years			30 years						15 years	[1]							15 years	[1]	20 years	[1]					10 years	[1]	15 years	[1]					5 years	[1]	20 years	[1]					5 years	[2]	25 years	[2]			10 years	25 years

[1] Depreciable lives of production facilities related to long-term customer supply contracts are matched to the contract lives.

[2] The depreciable lives for various types of distribution equipment are 10 to 25 years for cylinders, depending on the nature and properties of the product; 20 years for tanks; 7.5 years for customer stations; and 5 to 15 years for tractors and trailers.