Revenue Recognition (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Sales	$ 2,224.0	$ 2,259.0	$ 6,635.7	$ 6,631.3
Lease revenue percentage of total sales	5.00%		4.00%
Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 2,224.0	2,259.0	$ 6,635.7	6,631.3
Percent sales by supply mode	100.00%		100.00%
Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 955.3	948.7	$ 2,936.2	2,771.7
Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	494.6	561.1	1,513.2	1,638.6
Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	679.4	623.8	1,931.6	1,825.0
Industrial Gases - Global | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	57.9	101.1	179.9	335.8
Corporate and other | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	36.8	$ 24.3	74.8	$ 60.2
On-site | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 1,105.0		$ 3,449.7
Percent sales by supply mode	50.00%		52.00%
On-site | Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 537.1		$ 1,714.0
On-site | Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	165.0		565.8
On-site | Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	402.9		1,169.9
On-site | Industrial Gases - Global | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	0.0		0.0
On-site | Corporate and other | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	0.0		0.0
Merchant | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 1,024.3		$ 2,931.3
Percent sales by supply mode	46.00%		44.00%
Merchant | Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 418.2		$ 1,222.2
Merchant | Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	329.6		947.4
Merchant | Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	276.5		761.7
Merchant | Industrial Gases - Global | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	0.0		0.0
Merchant | Corporate and other | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	0.0		0.0
Sale of Equipment | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 94.7		$ 254.7
Percent sales by supply mode	4.00%		4.00%
Sale of Equipment | Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 0.0		$ 0.0
Sale of Equipment | Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	0.0		0.0
Sale of Equipment | Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	0.0		0.0
Sale of Equipment | Industrial Gases - Global | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	57.9		179.9
Sale of Equipment | Corporate and other | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 36.8		$ 74.8