Cost Reduction and Asset Actions (Narrative) (Details) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2017 USD ($)	[1]	Jun. 30, 2017 USD ($)	[1]	Mar. 31, 2017 USD ($)	[1]	Dec. 31, 2016 USD ($)	[1]	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($) position		Sep. 30, 2016 USD ($) position
Restructuring and Related Cost [Abstract]
Cost reduction and asset actions	$ 48.4		$ 42.7		$ 10.3		$ 50.0		$ 0.0	$ 151.4	[1]	$ 34.5
Cost Reduction Actions
Restructuring and Related Cost [Abstract]
Cost reduction and asset actions										154.8		34.5
Cost Reduction Actions | Industrial Gases - Americas
Restructuring and Related Cost [Abstract]
Cost reduction and asset actions										39.3
Cost Reduction Actions | Industrial Gases - EMEA
Restructuring and Related Cost [Abstract]
Cost reduction and asset actions										77.9
Cost Reduction Actions | Industrial Gases - Asia
Restructuring and Related Cost [Abstract]
Cost reduction and asset actions										0.9
Cost Reduction Actions | Industrial Gases - Global
Restructuring and Related Cost [Abstract]
Cost reduction and asset actions										2.5
Cost Reduction Actions | Corporate and other
Restructuring and Related Cost [Abstract]
Cost reduction and asset actions										34.2
Cost Reduction Actions | Severance and Other Benefits
Restructuring and Related Cost [Abstract]
Cost reduction and asset actions										$ 66.3		$ 34.5
Number of positions eliminated | position										625		610
Cost Reduction Actions | Asset Actions/Other
Restructuring and Related Cost [Abstract]
Cost reduction and asset actions										$ 88.5		$ 0.0
Business Realignment and Reorganization
Restructuring and Related Cost [Abstract]
Favorable restructuring reserve settlement										$ 3.4

[1] For additional information, refer to Note 5, Cost Reduction and Asset Actions.