Plant and Equipment, net (Major Classes of Plant and Equipment) (Details) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Property, Plant and Equipment [Line Items]
Plant and Equipment, at cost		$ 20,190.1	$ 19,462.8
Less: accumulated depreciation		11,337.4	10,717.7
Plant and equipment, net	[1]	8,852.7	8,745.1	$ 8,941.6
Land [Member]
Property, Plant and Equipment [Line Items]
Plant and Equipment, at cost		232.9	226.2
Building [Member]
Property, Plant and Equipment [Line Items]
Plant and Equipment, at cost		$ 1,119.8	1,080.2
Average useful life		30 years
Production Facility [Member]
Property, Plant and Equipment [Line Items]
Plant and Equipment, at cost		$ 13,267.3	12,819.5
Production Facility [Member] | Industrial Gases - Regional [Member]
Property, Plant and Equipment [Line Items]
Plant and Equipment, at cost	[2]	$ 12,372.1	11,873.8
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		$ 859.2	902.7
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		$ 36.0	43.0
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 and Other Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Plant and Equipment, at cost	[3]	$ 4,042.1	3,963.1
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
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
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Plant and Equipment, at cost		$ 1,528.0	$ 1,373.8

[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.