Cost Reduction and Asset Actions (Narrative) (Details) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2017 USD ($) position
Restructuring and Related Cost [Abstract]
Cost reduction and asset actions	$ 0.0	$ 50.0	$ 151.4
Asset Actions/Other | Industrial Gases - EMEA
Restructuring and Related Cost [Abstract]
Cost reduction and asset actions		$ 45.7
Cost Reduction Actions
Restructuring and Related Cost [Abstract]
Cost reduction and asset actions			154.8
Cash expenditures	13.6		36.9
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
Number of positions eliminated | position			625
Cash expenditures	13.5		$ 35.7
Cost Reduction Actions | Asset Actions/Other
Restructuring and Related Cost [Abstract]
Cost reduction and asset actions			88.5
Cash expenditures	$ 0.1		1.2
Business Realignment and Reorganization
Restructuring and Related Cost [Abstract]
Favorable restructuring reserve settlement			$ 3.4