Business Segment and Geographic Information (Schedule of Segment Reporting Information) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Sales	$ 10,323.0	$ 8,856.3	$ 8,918.9
Operating income (loss)	2,281.4	2,237.6	2,144.4
Depreciation and amortization	1,321.3	1,185.0	1,082.8
Equity affiliates' income	294.1	264.8	215.4
Expenditures for long-lived assets	2,464.2	2,509.0	1,989.7
Investment in net assets of and advances to equity affiliates	1,649.3	1,432.2
Total assets	26,859.2	25,168.5
Operating Segments
Segment Reporting Information [Line Items]
Sales	10,323.0	8,856.3	8,918.9
Operating income (loss)	2,267.8	2,203.8	2,169.8
Depreciation and amortization	1,321.3	1,185.0	1,082.8
Equity affiliates' income	294.1	231.0	215.4
Expenditures for long-lived assets	2,464.2	2,509.0	1,989.7
Investment in net assets of and advances to equity affiliates	1,649.3	1,432.2
Total assets	26,859.2	25,168.5
Industrial Gases - Americas | Operating Segments
Segment Reporting Information [Line Items]
Sales	4,167.6	3,630.7	3,873.5
Operating income (loss)	1,065.5	1,012.4	997.7
Depreciation and amortization	611.9	559.5	505.2
Equity affiliates' income	112.5	84.3	84.8
Expenditures for long-lived assets	909.6	1,264.7	545.8
Investment in net assets of and advances to equity affiliates	383.8	310.9
Total assets	7,092.5	6,610.1
Industrial Gases - EMEA | Operating Segments
Segment Reporting Information [Line Items]
Sales	2,444.9	1,926.3	2,002.5
Operating income (loss)	557.4	473.3	472.4
Depreciation and amortization	229.8	195.9	189.5
Equity affiliates' income	93.7	74.8	69.0
Expenditures for long-lived assets	371.3	327.6	216.3
Investment in net assets of and advances to equity affiliates	587.4	535.2
Total assets	4,353.2	3,917.0
Industrial Gases - Asia | Operating Segments
Segment Reporting Information [Line Items]
Sales	2,920.8	2,716.5	2,663.6
Operating income (loss)	838.3	870.3	864.2
Depreciation and amortization	444.4	399.4	361.5
Equity affiliates' income	81.4	61.0	58.4
Expenditures for long-lived assets	792.3	690.3	1,105.5
Investment in net assets of and advances to equity affiliates	608.1	539.7
Total assets	7,627.1	6,842.9
Industrial Gases - Global | Operating Segments
Segment Reporting Information [Line Items]
Sales	511.0	364.9	261.0
Operating income (loss)	(60.6)	(40.0)	(11.7)
Depreciation and amortization	10.9	9.6	8.6
Equity affiliates' income	6.5	10.9	3.2
Expenditures for long-lived assets	112.6	35.3	33.8
Investment in net assets of and advances to equity affiliates	70.0	46.4
Total assets	648.4	397.8
Corporate and other | Operating Segments
Segment Reporting Information [Line Items]
Sales	278.7	217.9	118.3
Operating income (loss)	(132.8)	(112.2)	(152.8)
Depreciation and amortization	24.3	20.6	18.0
Equity affiliates' income	0.0	0.0	0.0
Expenditures for long-lived assets	278.4	191.1	$ 88.3
Investment in net assets of and advances to equity affiliates	0.0	0.0
Total assets	$ 7,138.0	$ 7,400.7