Business Segment and Geographic Information (Schedule of Segment Reporting Information) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Sales	$ 2,320.1	$ 2,065.2	$ 2,216.3	$ 2,254.7	$ 2,283.2	$ 2,224.0	$ 2,187.7	$ 2,224.0	$ 8,856.3	$ 8,918.9	$ 8,930.2
Operating income (loss)	560.2	539.2	577.2	561.0	603.2	569.7	516.5	455.0	2,237.6	2,144.4	1,965.6
Depreciation and amortization									1,185.0	1,082.8	970.7
Equity affiliates' income	67.2	$ 51.2	$ 88.2	$ 58.2	59.9	$ 56.4	$ 46.2	$ 52.9	264.8	215.4	174.8
Expenditures for long-lived assets									2,509.0	1,989.7	1,568.4
Investment in net assets of and advances to equity affiliates	1,432.2				1,276.2				1,432.2	1,276.2
Total assets	25,168.5				18,942.8				25,168.5	18,942.8
Operating Segments
Segment Reporting Information [Line Items]
Sales									8,856.3	8,918.9	8,930.2
Operating income (loss)									2,203.8	2,169.8	1,941.5
Depreciation and amortization									1,185.0	1,082.8	970.7
Equity affiliates' income									231.0	215.4	203.3
Expenditures for long-lived assets									2,509.0	1,989.7	1,568.4
Investment in net assets of and advances to equity affiliates	1,432.2				1,276.2				1,432.2	1,276.2
Total assets	25,168.5				18,942.8				25,168.5	18,942.8
Industrial Gases - Americas | Operating Segments
Segment Reporting Information [Line Items]
Sales									3,630.7	3,873.5	3,758.8
Operating income (loss)									1,012.4	997.7	927.9
Depreciation and amortization									559.5	505.2	485.3
Equity affiliates' income									84.3	84.8	82.0
Expenditures for long-lived assets									1,264.7	545.8	546.5
Investment in net assets of and advances to equity affiliates	310.9				301.6				310.9	301.6
Total assets	6,610.1				5,832.2				6,610.1	5,832.2
Industrial Gases - EMEA | Operating Segments
Segment Reporting Information [Line Items]
Sales									1,926.3	2,002.5	2,193.3
Operating income (loss)									473.3	472.4	445.8
Depreciation and amortization									195.9	189.5	198.6
Equity affiliates' income									74.8	69.0	61.1
Expenditures for long-lived assets									327.6	216.3	163.1
Investment in net assets of and advances to equity affiliates	535.2				493.4				535.2	493.4
Total assets	3,917.0				3,250.8				3,917.0	3,250.8
Industrial Gases - Asia | Operating Segments
Segment Reporting Information [Line Items]
Sales									2,716.5	2,663.6	2,458.0
Operating income (loss)									870.3	864.2	689.9
Depreciation and amortization									399.4	361.5	265.8
Equity affiliates' income									61.0	58.4	58.3
Expenditures for long-lived assets									690.3	1,105.5	791.9
Investment in net assets of and advances to equity affiliates	539.7				445.5				539.7	445.5
Total assets	6,842.9				6,240.6				6,842.9	6,240.6
Industrial Gases - Global | Operating Segments
Segment Reporting Information [Line Items]
Sales									364.9	261.0	436.1
Operating income (loss)									(40.0)	(11.7)	53.9
Depreciation and amortization									9.6	8.6	8.1
Equity affiliates' income									10.9	3.2	1.9
Expenditures for long-lived assets									35.3	33.8	17.3
Investment in net assets of and advances to equity affiliates	46.4				35.7				46.4	35.7
Total assets	397.8				325.7				397.8	325.7
Corporate and other | Operating Segments
Segment Reporting Information [Line Items]
Sales									217.9	118.3	84.0
Operating income (loss)									(112.2)	(152.8)	(176.0)
Depreciation and amortization									20.6	18.0	12.9
Equity affiliates' income									0.0	0.0	0.0
Expenditures for long-lived assets									191.1	88.3	$ 49.6
Investment in net assets of and advances to equity affiliates	0.0				0.0				0.0	0.0
Total assets	$ 7,400.7				$ 3,293.5				$ 7,400.7	$ 3,293.5