Business Segment Information (Schedule of Segment Reporting Information) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Sep. 30, 2019
Segment Reporting Information [Line Items]
Sales		$ 2,216.3	$ 2,187.7	$ 4,471.0	$ 4,411.7
Operating income (loss)		577.2	516.5	1,138.2	971.5
Depreciation and amortization				583.9	520.1
Equity affiliates' income		88.2	46.2	146.4	99.1
Total assets		19,501.2		19,501.2		$ 18,942.8
Operating Segments
Segment Reporting Information [Line Items]
Sales	[1]	2,216.3	2,187.7	4,471.0	4,411.7
Operating income (loss)	[2]	543.4	516.5	1,104.4	1,000.5
Depreciation and amortization		294.7	262.1	583.9	520.1
Equity affiliates' income		54.4	46.2	112.6	99.1
Total assets		19,501.2		19,501.2		18,942.8
Industrial Gases - Americas | Operating Segments
Segment Reporting Information [Line Items]
Sales	[1]	932.4	991.7	1,868.6	1,980.9
Operating income (loss)	[2]	268.0	255.6	525.2	474.8
Depreciation and amortization		135.5	124.9	267.3	250.5
Equity affiliates' income		21.6	17.8	42.2	40.4
Total assets		5,933.7		5,933.7		5,832.2
Industrial Gases - EMEA | Operating Segments
Segment Reporting Information [Line Items]
Sales	[1]	492.7	494.4	991.4	1,018.6
Operating income (loss)	[2]	124.6	122.5	245.1	228.1
Depreciation and amortization		47.6	46.3	96.0	92.6
Equity affiliates' income		13.5	13.3	32.8	27.0
Total assets		3,378.8		3,378.8		3,250.8
Industrial Gases - Asia | Operating Segments
Segment Reporting Information [Line Items]
Sales	[1]	658.1	625.4	1,350.9	1,252.2
Operating income (loss)	[2]	209.1	199.7	437.6	401.5
Depreciation and amortization		104.1	84.9	205.7	164.8
Equity affiliates' income		13.8	13.8	30.7	30.0
Total assets		6,489.7		6,489.7		6,240.6
Industrial Gases - Global | Operating Segments
Segment Reporting Information [Line Items]
Sales	[1]	79.3	53.8	171.9	122.0
Operating income (loss)	[2]	(19.8)	(12.2)	(16.2)	(8.3)
Depreciation and amortization		2.4	2.0	4.8	4.1
Equity affiliates' income		5.5	1.3	6.9	1.7
Total assets		438.1		438.1		325.7
Corporate and other | Operating Segments
Segment Reporting Information [Line Items]
Sales	[1]	53.8	22.4	88.2	38.0
Operating income (loss)	[2]	(38.5)	(49.1)	(87.3)	(95.6)
Depreciation and amortization		5.1	4.0	10.1	8.1
Equity affiliates' income		0.0	$ 0.0	0.0	$ 0.0
Total assets		$ 3,260.9		$ 3,260.9		$ 3,293.5

[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 reflect as an intersegment sale.

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