Revenue Recognition (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Sales	$ 2,187.7	$ 2,155.7	$ 4,411.7	$ 4,372.3
Lease revenue percentage of total sales	4.00%		4.00%
Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 2,187.7	2,155.7	$ 4,411.7	4,372.3
Percent sales by supply mode	100.00%		100.00%
Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 991.7	913.2	$ 1,980.9	1,823.0
Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	494.4	561.6	1,018.6	1,077.5
Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	625.4	557.6	1,252.2	1,201.2
Industrial Gases - Global | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	53.8	101.7	122.0	234.7
Corporate and other | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	22.4	$ 21.6	38.0	$ 35.9
On-site | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 1,145.5		$ 2,344.7
Percent sales by supply mode	52.00%		53.00%
On-site | Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 580.9		$ 1,176.9
On-site | Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	178.6		400.8
On-site | Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	386.0		767.0
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	$ 966.0		$ 1,907.0
Percent sales by supply mode	44.00%		43.00%
Merchant | Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 410.8		$ 804.0
Merchant | Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	315.8		617.8
Merchant | Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	239.4		485.2
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	$ 76.2		$ 160.0
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	53.8		122.0
Sale of Equipment | Corporate and other | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	$ 22.4		$ 38.0