Revenue Recognition (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Sales	$ 2,375.2	$ 2,254.7
Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 2,375.2	$ 2,254.7
Percent sales by supply mode	100.00%	100.00%
Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 933.0	$ 936.2
Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	563.0	498.7
Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	717.5	692.8
Industrial Gases - Global | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	104.5	92.6
Corporate and other | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	57.2	34.4
On-site | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 1,144.9	$ 1,124.2
Percent sales by supply mode	48.00%	50.00%
On-site | Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 541.3	$ 534.5
On-site | Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	188.7	171.4
On-site | Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	414.9	418.3
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	$ 1,068.6	$ 1,003.5
Percent sales by supply mode	45.00%	44.00%
Merchant | Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 391.7	$ 401.7
Merchant | Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	374.3	327.3
Merchant | Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	302.6	274.5
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	$ 161.7	$ 127.0
Percent sales by supply mode	7.00%	6.00%
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	104.5	92.6
Sale of Equipment | Corporate and other | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 57.2	$ 34.4