Revenue Recognition (Disaggregation of Revenue) (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Sales		$ 2,283.2	$ 2,224.0	$ 2,187.7	$ 2,224.0	$ 2,298.9	$ 2,259.0	$ 2,155.7	$ 2,216.6	$ 8,918.9	$ 8,930.2	$ 8,187.6
Lease revenue percentage of total sales										5.00%
Operating Segments
Disaggregation of Revenue [Line Items]
Sales	[1]									$ 8,918.9	8,930.2	8,187.6
Percent sales by supply mode										100.00%
Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	[1]									$ 3,873.5	3,758.8	3,637.0
Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	[1]									2,002.5	2,193.3	1,780.4
Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	[1]									2,663.6	2,458.0	1,964.7
Industrial Gases - Global | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	[1]									261.0	436.1	722.9
Corporate and other | Operating Segments
Disaggregation of Revenue [Line Items]
Sales	[1]									118.3	$ 84.0	$ 82.6
On-site | Operating Segments
Disaggregation of Revenue [Line Items]
Sales										$ 4,581.6
Percent sales by supply mode										52.00%
On-site | Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales										$ 2,230.6
On-site | Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales										728.4
On-site | Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales										1,622.6
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										$ 3,958.0
Percent sales by supply mode										44.00%
Merchant | Industrial Gases - Americas | Operating Segments
Disaggregation of Revenue [Line Items]
Sales										$ 1,642.9
Merchant | Industrial Gases - EMEA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales										1,274.1
Merchant | Industrial Gases - Asia | Operating Segments
Disaggregation of Revenue [Line Items]
Sales										1,041.0
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										$ 379.3
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										261.0
Sale of Equipment | Corporate and other | Operating Segments
Disaggregation of Revenue [Line Items]
Sales										$ 118.3

[1] The sales information noted above relates to external customers only. All intersegment sales are eliminated in consolidation. Intersegment sales are generally transacted at market pricing. We generally do not have intersegment sales from our regional industrial gases businesses. Equipment manufactured for our regional industrial gases segments are generally transferred at cost and are not reflected as an intersegment sale.