Revenue Recognition (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Sales	$ 2,224.0	$ 2,216.6
Lease revenue percentage of total sales	4.00%
Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 2,224.0	2,216.6
Percent sales by supply mode	100.00%
Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 989.2	909.8
Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	524.2	515.9
Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	626.8	643.6
Industrial Gases - Global | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	68.2	133.0
Corporate and other | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	15.6	$ 14.3
On-site | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 1,199.2
Percent sales by supply mode	54.00%
On-site | Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 596.0
On-site | Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	222.2
On-site | Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	381.0
On-site | Industrial Gases - Global | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	0.0
On-site | Corporate and other | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	0.0
Merchant | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 941.0
Percent sales by supply mode	42.00%
Merchant | Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 393.2
Merchant | Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	302.0
Merchant | Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	245.8
Merchant | Industrial Gases - Global | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	0.0
Merchant | Corporate and other | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	0.0
Sale of Equipment | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 83.8
Percent sales by supply mode	4.00%
Sale of Equipment | Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 0.0
Sale of Equipment | Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	0.0
Sale of Equipment | Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	0.0
Sale of Equipment | Industrial Gases - Global | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	68.2
Sale of Equipment | Corporate and other | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 15.6