Business Segment and Geographic Information (Schedule of Segment Reporting Information) (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
Segment Reporting Information [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
Operating income (loss)		603.2	569.7	516.5	455.0	533.7	515.8	455.4	460.7	2,144.4	1,965.6	1,440.0
Depreciation and amortization										1,082.8	970.7	865.8
Equity affiliates' income		59.9	$ 56.4	$ 46.2	$ 52.9	59.2	$ 58.1	$ 43.7	$ 13.8	215.4	174.8	80.1
Expenditures for long-lived assets										1,989.7	1,568.4	1,039.7
Investment in net assets of and advances to equity affiliates		1,276.2				1,277.2				1,276.2	1,277.2
Total assets		18,942.8				19,178.3				18,942.8	19,178.3
Operating Segments
Segment Reporting Information [Line Items]
Sales	[1]									8,918.9	8,930.2	8,187.6
Operating income (loss)	[2]									2,169.8	1,941.5	1,773.8
Depreciation and amortization										1,082.8	970.7	865.8
Equity affiliates' income	[2]									215.4	203.3	159.6
Expenditures for long-lived assets										1,989.7	1,568.4	1,039.7
Investment in net assets of and advances to equity affiliates		1,276.2				1,277.2				1,276.2	1,277.2
Total assets		18,942.8				19,178.3				18,942.8	19,178.3
Industrial Gases - Americas | Operating Segments
Segment Reporting Information [Line Items]
Sales	[1]									3,873.5	3,758.8	3,637.0
Operating income (loss)	[2]									997.7	927.9	946.1
Depreciation and amortization										505.2	485.3	464.4
Equity affiliates' income	[2]									84.8	82.0	58.1
Expenditures for long-lived assets										545.8	546.5	427.2
Investment in net assets of and advances to equity affiliates		301.6				312.1				301.6	312.1
Total assets		5,832.2				5,904.0				5,832.2	5,904.0
Industrial Gases - EMEA | Operating Segments
Segment Reporting Information [Line Items]
Sales	[1]									2,002.5	2,193.3	1,780.4
Operating income (loss)	[2]									472.4	445.8	395.5
Depreciation and amortization										189.5	198.6	177.1
Equity affiliates' income	[2]									69.0	61.1	47.1
Expenditures for long-lived assets										216.3	163.1	143.2
Investment in net assets of and advances to equity affiliates		493.4				503.3				493.4	503.3
Total assets		3,250.8				3,280.4				3,250.8	3,280.4
Industrial Gases - Asia | Operating Segments
Segment Reporting Information [Line Items]
Sales	[1]									2,663.6	2,458.0	1,964.7
Operating income (loss)	[2]									864.2	689.9	532.6
Depreciation and amortization										361.5	265.8	203.2
Equity affiliates' income	[2]									58.4	58.3	53.5
Expenditures for long-lived assets										1,105.5	791.9	337.8
Investment in net assets of and advances to equity affiliates		445.5				445.6				445.5	445.6
Total assets		6,240.6				5,899.5				6,240.6	5,899.5
Industrial Gases - Global | Operating Segments
Segment Reporting Information [Line Items]
Sales	[1]									261.0	436.1	722.9
Operating income (loss)	[2]									(11.7)	53.9	71.1
Depreciation and amortization										8.6	8.1	8.9
Equity affiliates' income	[2]									3.2	1.9	0.9
Expenditures for long-lived assets										33.8	17.3	25.6
Investment in net assets of and advances to equity affiliates		35.7				16.2				35.7	16.2
Total assets		325.7				240.1				325.7	240.1
Corporate and other | Operating Segments
Segment Reporting Information [Line Items]
Sales	[1]									118.3	84.0	82.6
Operating income (loss)	[2]									(152.8)	(176.0)	(171.5)
Depreciation and amortization										18.0	12.9	12.2
Equity affiliates' income	[2]									0.0	0.0	0.0
Expenditures for long-lived assets										88.3	49.6	$ 105.9
Investment in net assets of and advances to equity affiliates		0.0				0.0				0.0	0.0
Total assets		$ 3,293.5				$ 3,854.3				$ 3,293.5	$ 3,854.3

[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.

[2] Refer to the Reconciliations to Consolidated Results section below.