Business Restructuring and Cost Reduction Actions (Narrative) (Details) $ / shares in Units, $ in Millions	3 Months Ended																	12 Months Ended
	Sep. 30, 2015 USD ($)	[1]	Jun. 30, 2015 USD ($)	[1]	Mar. 31, 2015 USD ($)	[1]	Dec. 31, 2014 USD ($)	[1]	Sep. 30, 2014 USD ($) Employees $ / shares		Jun. 30, 2014 USD ($)	[1]	Mar. 31, 2014 USD ($)	[1]	Dec. 31, 2013 USD ($)	[1]	Sep. 30, 2013 USD ($) $ / shares	Sep. 30, 2015 USD ($) Employees $ / shares		Sep. 30, 2014 USD ($)		Sep. 30, 2013 USD ($)
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions	$ 61.7		$ 58.2		$ 55.4		$ 32.4		$ 12.7	[1]	$ 0.0		$ 0.0		$ 0.0			$ 207.7	[1]	$ 12.7	[1]	$ 231.6
Business Realignment and Reorganization [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions									12.7									207.7		12.7
Business restructuring and cost reduction actions, after-tax									$ 8.2									$ 153.2
Business restructuring and cost reduction actions, per share | $ / shares									$ 0.04									$ 0.71
Number of positions to be eliminated | Employees									50									2,000
Business Realignment and Reorganization [Member] | Industrial Gases Americas [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions																		$ 31.7		2.9
Business Realignment and Reorganization [Member] | Industrial Gases EMEA [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions																		52.2		3.1
Business Realignment and Reorganization [Member] | Industrial Gases Asia [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions																		10.3		1.5
Business Realignment and Reorganization [Member] | Industrial Gases Global [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions																		37.0		1.5
Business Realignment and Reorganization [Member] | Materials Technologies [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions																		27.6		1.6
Business Realignment and Reorganization [Member] | Corporate and Other [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions																		48.9		2.1
Business Realignment and Reorganization [Member] | Asset Actions [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions																		55.8		0.0
Business Realignment and Reorganization [Member] | Severance And Other Benefits [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions																		$ 151.9		$ 12.7
Plan 2013 [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions																	$ 231.6					231.6
Business restructuring and cost reduction actions, after-tax																	$ 157.9
Business restructuring and cost reduction actions, per share | $ / shares																	$ 0.74
Plan 2013 [Member] | Industrial Gases Americas [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions																						26.6
Plan 2013 [Member] | Industrial Gases EMEA [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions																						26.2
Plan 2013 [Member] | Industrial Gases Asia [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions																						24.1
Plan 2013 [Member] | Industrial Gases Global [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions																						0.7
Plan 2013 [Member] | Materials Technologies [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions																						133.3
Plan 2013 [Member] | Corporate and Other [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions																						20.7
Plan 2013 [Member] | Asset Actions [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions																						100.4
Plan 2013 [Member] | Severance And Other Benefits [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions																						71.9
Plan 2013 [Member] | Contract Actions [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions																						$ 59.3

[1] For additional information, see Note 5, Business Restructuring and Cost Reduction Actions.