Business Segment Information (Schedule of Segment Reporting Information) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2017
Segment Reporting Information [Line Items]
Sales	$ 2,259.0	$ 2,121.9	$ 6,631.3	$ 5,984.5
Operating income (loss)	515.8	258.7	1,431.9	982.6
Depreciation and amortization			713.5	634.8
Equity affiliates' income (loss)	58.1	(36.9)	115.6	35.3
Total assets	19,206.0		19,206.0		$ 18,467.2
Operating Segments
Segment Reporting Information [Line Items]
Sales	2,259.0	2,121.9	6,631.3	5,984.5
Operating income (loss)	515.8	463.5	1,431.9	1,280.2
Depreciation and amortization	245.6	216.9	713.5	634.8
Equity affiliates' income (loss)	58.1	42.6	148.1	114.8
Total assets	19,206.0		19,206.0		18,457.0
Industrial Gases - Americas \| Operating Segments
Segment Reporting Information [Line Items]
Sales	948.7	930.1	2,771.7	2,684.1
Operating income (loss)	237.1	234.9	676.6	681.4
Depreciation and amortization	120.5	117.0	360.6	344.8
Equity affiliates' income (loss)	24.1	14.1	59.6	41.8
Total assets	5,857.7		5,857.7		5,840.8
Industrial Gases - EMEA \| Operating Segments
Segment Reporting Information [Line Items]
Sales	561.1	451.7	1,638.6	1,265.6
Operating income (loss)	118.8	96.2	340.0	274.8
Depreciation and amortization	49.8	45.1	149.6	128.9
Equity affiliates' income (loss)	17.5	15.7	41.7	33.5
Total assets	3,311.8		3,311.8		3,276.1
Industrial Gases - Asia \| Operating Segments
Segment Reporting Information [Line Items]
Sales	623.8	538.3	1,825.0	1,412.5
Operating income (loss)	185.5	149.5	509.7	380.2
Depreciation and amortization	69.5	49.6	188.9	145.6
Equity affiliates' income (loss)	15.1	12.5	44.7	38.9
Total assets	5,880.0		5,880.0		4,412.1
Industrial Gases - Global \| Operating Segments
Segment Reporting Information [Line Items]
Sales	101.1	187.4	335.8	551.8
Operating income (loss)	19.8	27.8	41.4	58.7
Depreciation and amortization	2.3	2.3	5.8	6.0
Equity affiliates' income (loss)	1.4	0.3	2.1	0.6
Total assets	267.9		267.9		279.6
Corporate and other \| Operating Segments
Segment Reporting Information [Line Items]
Sales	24.3	14.4	60.2	70.5
Operating income (loss)	(45.4)	(44.9)	(135.8)	(114.9)
Depreciation and amortization	3.5	2.9	8.6	9.5
Equity affiliates' income (loss)	0.0	$ 0.0	0.0	$ 0.0
Total assets	$ 3,888.6		$ 3,888.6		$ 4,648.4

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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