Business Segment and Geographic Information (Schedule of Segment Reporting Information) (Details) - USD ($) $ in Millions	3 Months Ended											12 Months Ended
	Sep. 30, 2018		Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017		Sep. 30, 2017	Jun. 30, 2017		Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2018		Sep. 30, 2017		Sep. 30, 2016	Oct. 01, 2018
Segment Reporting Information [Line Items]
Sales	$ 2,298.9		$ 2,259.0	$ 2,155.7	$ 2,216.6		$ 2,203.1	$ 2,121.9		$ 1,980.1	$ 1,882.5	$ 8,930.2		$ 8,187.6		$ 7,503.7
Operating income (loss)	533.7		515.8	455.4	460.7		457.4	258.7		395.6	328.3	1,965.6		1,440.0		1,535.1
Depreciation and amortization												970.7		865.8		854.6
Equity affiliates' income (loss)	59.2	[1]	$ 58.1	$ 43.7	$ 13.8	[1]	44.8	$ (36.9)	[2]	$ 34.2	$ 38.0	174.8	[1]	80.1	[2]	147.0
Expenditures for long-lived assets												1,568.4		1,039.7		907.7
Investment in net assets of and advances to equity affiliates	1,277.2						1,286.9					1,277.2		1,286.9
Total assets	19,178.3						18,467.2					19,178.3		18,467.2		18,028.6	$ 19,204.5
Operating Segments
Segment Reporting Information [Line Items]
Sales												8,930.2		8,187.6		7,503.7
Operating income (loss)												1,941.5		1,773.8		1,620.2
Depreciation and amortization												970.7		865.8		854.6
Equity affiliates' income (loss)												203.3		159.6		147.0
Expenditures for long-lived assets												1,568.4		1,039.7		907.7
Investment in net assets of and advances to equity affiliates	1,277.2						1,286.9					1,277.2		1,286.9		1,283.6
Total assets	19,178.3						18,457.0					19,178.3		18,457.0		16,060.1
Industrial Gases - Americas | Operating Segments
Segment Reporting Information [Line Items]
Sales												3,758.8		3,637.0		3,344.1
Operating income (loss)												927.9		946.1		891.3
Depreciation and amortization												485.3		464.4		443.6
Equity affiliates' income (loss)												82.0		58.1		52.7
Expenditures for long-lived assets												546.5		427.2		406.6
Investment in net assets of and advances to equity affiliates	312.1						287.5					312.1		287.5		250.6
Total assets	5,904.0						5,840.8					5,904.0		5,840.8		5,896.7
Industrial Gases - EMEA | Operating Segments
Segment Reporting Information [Line Items]
Sales												2,193.3		1,780.4		1,704.4
Operating income (loss)												445.8		395.5		387.0
Depreciation and amortization												198.6		177.1		185.7
Equity affiliates' income (loss)												61.1		47.1		36.5
Expenditures for long-lived assets												163.1		143.2		159.5
Investment in net assets of and advances to equity affiliates	503.3						508.6					503.3		508.6		580.5
Total assets	3,280.4						3,276.1					3,280.4		3,276.1		3,178.6
Industrial Gases - Asia | Operating Segments
Segment Reporting Information [Line Items]
Sales												2,458.0		1,964.7		1,720.4
Operating income (loss)												689.9		532.6		452.8
Depreciation and amortization												265.8		203.2		197.9
Equity affiliates' income (loss)												58.3		53.5		57.8
Expenditures for long-lived assets												791.9		337.8		313.3
Investment in net assets of and advances to equity affiliates	445.6						471.8					445.6		471.8		442.5
Total assets	5,899.5						4,412.1					5,899.5		4,412.1		4,232.7
Industrial Gases - Global | Operating Segments
Segment Reporting Information [Line Items]
Sales												436.1		722.9		498.8
Operating income (loss)												53.9		71.1		(21.5)
Depreciation and amortization												8.1		8.9		7.9
Equity affiliates' income (loss)												1.9		0.9		0.0
Expenditures for long-lived assets												17.3		25.6		6.0
Investment in net assets of and advances to equity affiliates	16.2						19.0					16.2		19.0		10.0
Total assets	240.1						279.6					240.1		279.6		367.6
Corporate and other | Operating Segments
Segment Reporting Information [Line Items]
Sales												84.0		82.6		236.0
Operating income (loss)												(176.0)		(171.5)		(89.4)
Depreciation and amortization												12.9		12.2		19.5
Equity affiliates' income (loss)												0.0		0.0		0.0
Expenditures for long-lived assets												49.6		105.9		22.3
Investment in net assets of and advances to equity affiliates	0.0						0.0					0.0		0.0		0.0
Total assets	$ 3,854.3						$ 4,648.4					$ 3,854.3		$ 4,648.4		$ 2,384.5

[1] Includes the impacts of the Tax Act. For additional information, refer to Note 22, Income Taxes.

[2] Includes the impact of an other-than-temporary impairment of an investment in an equity affiliate. For additional information, refer to Note 8, Summarized Financial Information of Equity Affiliates.