Business Restructuring and Cost Reduction Actions (Narrative) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014	Sep. 30, 2014 Employees	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2013
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions	$ 55.4	$ 0	$ 87.8	$ 0
Business Realignment and Reorganization [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions	55.4		87.8		12.7
Business restructuring and cost reduction actions, after-tax	38.2		59.9		8.2
Business restructuring and cost reduction actions, per share	$ 0.18		$ 0.27		$ 0.04
Number of positions to be eliminated			1,100		50
Business Realignment and Reorganization [Member] | Industrial Gases - Americas [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions			13.8		2.9
Business Realignment and Reorganization [Member] | Industrial Gases - EMEA [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions			29.5		3.1
Business Realignment and Reorganization [Member] | Industrial Gases - Asia [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions			7.5		1.5
Business Realignment and Reorganization [Member] | Industrial Gases - Global [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions			3.1		1.5
Business Realignment and Reorganization [Member] | Materials Technologies [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions			10.6		1.6
Business Realignment and Reorganization [Member] | Corporate and Other [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions			23.3		2.1
Business Realignment and Reorganization [Member] | Severance And Other Benefits [Member]
Restructuring and Related Cost [Line Items]
Business restructuring and cost reduction actions			87.8			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							$ 0.74
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