Business Segment Information (Schedule of Segment Reporting Information) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Oct. 01, 2018	Sep. 30, 2018
Segment Reporting Information [Line Items]
Sales	$ 2,187.7	$ 2,155.7	$ 4,411.7	$ 4,372.3
Operating income (loss)	516.5	455.4	971.5	916.1
Depreciation and amortization			520.1	467.9
Equity affiliates' income	46.2	43.7	99.1	57.5
Total assets	19,244.5		19,244.5		$ 19,204.5	$ 19,178.3
Operating Segments
Segment Reporting Information [Line Items]
Sales	2,187.7	2,155.7	4,411.7	4,372.3
Operating income (loss)	516.5	455.4	1,000.5	916.1
Depreciation and amortization	262.1	240.0	520.1	467.9
Equity affiliates' income	46.2	43.7	99.1	90.0
Total assets	19,244.5		19,244.5			19,178.3
Industrial Gases - Americas \| Operating Segments
Segment Reporting Information [Line Items]
Sales	991.7	913.2	1,980.9	1,823.0
Operating income (loss)	255.6	222.3	474.8	439.5
Depreciation and amortization	124.9	122.3	250.5	240.1
Equity affiliates' income	17.8	16.9	40.4	35.5
Total assets	5,885.6		5,885.6			5,904.0
Industrial Gases - EMEA \| Operating Segments
Segment Reporting Information [Line Items]
Sales	494.4	561.6	1,018.6	1,077.5
Operating income (loss)	122.5	116.7	228.1	221.2
Depreciation and amortization	46.3	50.7	92.6	99.8
Equity affiliates' income	13.3	11.1	27.0	24.2
Total assets	3,333.7		3,333.7			3,280.4
Industrial Gases - Asia \| Operating Segments
Segment Reporting Information [Line Items]
Sales	625.4	557.6	1,252.2	1,201.2
Operating income (loss)	199.7	148.7	401.5	324.2
Depreciation and amortization	84.9	62.6	164.8	119.4
Equity affiliates' income	13.8	15.4	30.0	29.6
Total assets	6,167.0		6,167.0			5,899.5
Industrial Gases - Global \| Operating Segments
Segment Reporting Information [Line Items]
Sales	53.8	101.7	122.0	234.7
Operating income (loss)	(12.2)	12.1	(8.3)	21.6
Depreciation and amortization	2.0	1.9	4.1	3.5
Equity affiliates' income	1.3	0.3	1.7	0.7
Total assets	257.8		257.8			240.1
Corporate and other \| Operating Segments
Segment Reporting Information [Line Items]
Sales	22.4	21.6	38.0	35.9
Operating income (loss)	(49.1)	(44.4)	(95.6)	(90.4)
Depreciation and amortization	4.0	2.5	8.1	5.1
Equity affiliates' income	0.0	$ 0.0	0.0	$ 0.0
Total assets	$ 3,600.4		$ 3,600.4			$ 3,854.3

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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