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