Revenue Recognition (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Sales	$ 2,065.2	$ 2,224.0	$ 6,536.2	$ 6,635.7
Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 2,065.2	$ 2,224.0	$ 6,536.2	$ 6,635.7
Percent sales by supply mode	100.00%	100.00%	100.00%	100.00%
Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 849.9	$ 955.3	$ 2,718.5	$ 2,936.2
Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	429.7	494.6	1,421.1	1,513.2
Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	651.9	679.4	2,002.8	1,931.6
Industrial Gases - Global | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	77.6	57.9	249.5	179.9
Corporate and other | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	56.1	36.8	144.3	74.8
On-site | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 1,017.7	$ 1,105.0	$ 3,244.0	$ 3,449.7
Percent sales by supply mode	49.00%	50.00%	50.00%	52.00%
On-site | Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 487.4	$ 537.1	$ 1,538.1	$ 1,714.0
On-site | Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	143.2	165.0	474.9	565.8
On-site | Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	387.1	402.9	1,231.0	1,169.9
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	$ 913.8	$ 1,024.3	$ 2,898.4	$ 2,931.3
Percent sales by supply mode	44.00%	46.00%	44.00%	44.00%
Merchant | Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 362.5	$ 418.2	$ 1,180.4	$ 1,222.2
Merchant | Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	286.5	329.6	946.2	947.4
Merchant | Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	264.8	276.5	771.8	761.7
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	$ 133.7	$ 94.7	$ 393.8	$ 254.7
Percent sales by supply mode	7.00%	4.00%	6.00%	4.00%
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	77.6	57.9	249.5	179.9
Sale of Equipment | Corporate and other | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 56.1	$ 36.8	$ 144.3	$ 74.8