Business Restructuring and Cost Reduction 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, 2016 USD ($)	[1]	Jun. 30, 2016 USD ($)	[1]	Mar. 31, 2016 USD ($)	[1]	Dec. 31, 2015 USD ($)	[1]	Sep. 30, 2014 USD ($) position	Sep. 30, 2017 USD ($) position		Sep. 30, 2016 USD ($) position		Sep. 30, 2015 USD ($) position	Sep. 30, 2014 USD ($)
Restructuring and Related Cost [Abstract]
Business restructuring and cost reduction actions	$ 48.4		$ 42.7		$ 10.3		$ 50.0		$ 10.6		$ 13.2		$ 10.7		$ 0.0			$ 151.4	[1]	$ 34.5	[1]	$ 180.1
Cost Reduction Actions
Restructuring and Related Cost [Abstract]
Business restructuring and cost reduction actions																		154.8		34.5
Cost Reduction Actions | Industrial Gases - Americas
Restructuring and Related Cost [Abstract]
Business restructuring and cost reduction actions																		39.3
Cost Reduction Actions | Industrial Gases - EMEA
Restructuring and Related Cost [Abstract]
Business restructuring and cost reduction actions																		77.9
Cost Reduction Actions | Industrial Gases - Asia
Restructuring and Related Cost [Abstract]
Business restructuring and cost reduction actions																		0.9
Cost Reduction Actions | Industrial Gases - Global
Restructuring and Related Cost [Abstract]
Business restructuring and cost reduction actions																		2.5
Cost Reduction Actions | Corporate and Other
Restructuring and Related Cost [Abstract]
Business restructuring and cost reduction actions																		34.2
Cost Reduction Actions | Severance and Other Benefits
Restructuring and Related Cost [Abstract]
Business restructuring and cost reduction actions																		$ 66.3		$ 34.5
Number of positions eliminated | position																		625		610
Cost Reduction Actions | Asset Actions/Other
Restructuring and Related Cost [Abstract]
Business restructuring and cost reduction actions																		$ 88.5		$ 0.0
Business Realignment and Reorganization
Restructuring and Related Cost [Abstract]
Business restructuring and cost reduction actions																						180.1	$ 11.1
Favorable restructuring reserve settlement																		3.4
Business Realignment and Reorganization | Industrial Gases - Americas
Restructuring and Related Cost [Abstract]
Business restructuring and cost reduction actions																						31.7
Business Realignment and Reorganization | Industrial Gases - EMEA
Restructuring and Related Cost [Abstract]
Business restructuring and cost reduction actions																						52.2
Business Realignment and Reorganization | Industrial Gases - Asia
Restructuring and Related Cost [Abstract]
Business restructuring and cost reduction actions																						10.3
Business Realignment and Reorganization | Industrial Gases - Global
Restructuring and Related Cost [Abstract]
Business restructuring and cost reduction actions																						37.0
Business Realignment and Reorganization | Corporate and Other
Restructuring and Related Cost [Abstract]
Business restructuring and cost reduction actions																						48.9
Business Realignment and Reorganization | Severance and Other Benefits
Restructuring and Related Cost [Abstract]
Business restructuring and cost reduction actions																	$ 11.1					$ 131.5	11.1
Favorable restructuring reserve settlement																		0.0
Number of positions eliminated | position																	40					1,700
Business Realignment and Reorganization | Asset Actions/Other
Restructuring and Related Cost [Abstract]
Business restructuring and cost reduction actions																						$ 48.6	$ 0.0
Favorable restructuring reserve settlement																		$ 3.4

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