Plant and Equipment, net (Major Classes of Plant and Equipment) (Details) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Property, Plant and Equipment [Line Items]
Plant and Equipment, at cost		$ 20,354.6	$ 20,223.5
Less: accumulated depreciation		10,717.7	10,691.4
Plant and equipment, net	[1]	9,636.9	9,532.1	$ 8,974.0
Land [Member]
Property, Plant and Equipment [Line Items]
Plant and Equipment, at cost		226.2	236.6
Building [Member]
Property, Plant and Equipment [Line Items]
Plant and Equipment, at cost		$ 1,080.2	1,105.0
Average useful life		30 years
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Plant and Equipment, at cost		$ 2,265.6	1,762.9
Production Facility [Member]
Property, Plant and Equipment [Line Items]
Plant and Equipment, at cost		12,819.5	12,943.7
Production Facility [Member] | Industrial Gases - Regional [Member]
Property, Plant and Equipment [Line Items]
Plant and Equipment, at cost	[2]	$ 11,873.8	12,002.4
Production Facility [Member] | Industrial Gases - Regional [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average useful life		10 years
Production Facility [Member] | Industrial Gases - Regional [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average useful life		20 years
Production Facility [Member] | Materials Technologies [Member]
Property, Plant and Equipment [Line Items]
Plant and Equipment, at cost		$ 902.7	849.1
Production Facility [Member] | Materials Technologies [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average useful life		10 years
Production Facility [Member] | Materials Technologies [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average useful life		15 years
Production Facility [Member] | Other [Member]
Property, Plant and Equipment [Line Items]
Plant and Equipment, at cost		$ 43.0	92.2
Production Facility [Member] | Other [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average useful life		5 years
Production Facility [Member] | Other [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average useful life		20 years
Distribution equipment | Cylinders [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average useful life		10 years
Distribution equipment | Cylinders [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average useful life		25 years
Distribution equipment | Tanks [Member]
Property, Plant and Equipment [Line Items]
Average useful life		20 years
Distribution equipment | Customer Stations [Member]
Property, Plant and Equipment [Line Items]
Average useful life		7 years 6 months
Distribution equipment | Tractors and Trailers [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average useful life		5 years
Distribution equipment | Tractors and Trailers [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average useful life		15 years
Distribution and Other Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Plant and Equipment, at cost	[3]	$ 3,963.1	$ 4,175.3
Distribution and Other Machinery and Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average useful life		5 years
Distribution and Other Machinery and Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average useful life		25 years

[1] Long-lived assets include plant and equipment, net.

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

[3] 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.