Revenue Recognition (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Sales	$ 2,604.7	$ 2,065.2	$ 7,481.9	$ 6,536.2
Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 2,604.7	$ 2,065.2	$ 7,481.9	$ 6,536.2
Percent sales by supply mode	100.00%	100.00%	100.00%	100.00%
Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 1,063.3	$ 849.9	$ 3,052.4	$ 2,718.5
Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	623.3	429.7	1,770.9	1,421.1
Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	751.8	651.9	2,166.8	2,002.8
Industrial Gases - Global | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	99.1	77.6	301.5	249.5
Corporate and other | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	67.2	56.1	190.3	144.3
On-site | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 1,272.8	$ 1,017.7	$ 3,672.7	$ 3,244.0
Percent sales by supply mode	49.00%	49.00%	49.00%	50.00%
On-site | Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 607.9	$ 487.4	$ 1,785.9	$ 1,538.1
On-site | Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	222.1	143.2	613.1	474.9
On-site | Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	442.8	387.1	1,273.7	1,231.0
On-site | Industrial Gases - Global | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	0.0	0.0	0.0	0.0
On-site | Corporate and other | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	0.0	0.0	0.0	0.0
Merchant | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 1,165.6	$ 913.8	$ 3,317.4	$ 2,898.4
Percent sales by supply mode	45.00%	44.00%	44.00%	44.00%
Merchant | Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 455.4	$ 362.5	$ 1,266.5	$ 1,180.4
Merchant | Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	401.2	286.5	1,157.8	946.2
Merchant | Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	309.0	264.8	893.1	771.8
Merchant | Industrial Gases - Global | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	0.0	0.0	0.0	0.0
Merchant | Corporate and other | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	0.0	0.0	0.0	0.0
Sale of Equipment | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 166.3	$ 133.7	$ 491.8	$ 393.8
Percent sales by supply mode	6.00%	7.00%	7.00%	6.00%
Sale of Equipment | Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 0.0	$ 0.0	$ 0.0	$ 0.0
Sale of Equipment | Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	0.0	0.0	0.0	0.0
Sale of Equipment | Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	0.0	0.0	0.0	0.0
Sale of Equipment | Industrial Gases - Global | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	99.1	77.6	301.5	249.5
Sale of Equipment | Corporate and other | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 67.2	$ 56.1	$ 190.3	$ 144.3