Business Segment Information (Schedule of Segment Reporting Information) (Details) $ in Millions		3 Months Ended		6 Months Ended
		Mar. 31, 2025 USD ($)	Mar. 31, 2024 USD ($)	Mar. 31, 2025 USD ($) segment	Mar. 31, 2024 USD ($)	Sep. 30, 2024 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment				2
Sales		$ 2,916.2	$ 2,930.2	$ 5,847.7	$ 5,927.6
Operating income (loss)		(2,328.0)	637.2	(1,684.4)	1,304.1
Depreciation and amortization				750.4	710.0
Equity affiliates' income		145.5	143.3	296.1	301.7
Total Assets	[1]	38,872.9		38,872.9		$ 39,574.6
Operating Segments
Segment Reporting Information [Line Items]
Sales		2,916.2	2,930.2	5,847.7	5,927.6
Operating income (loss)		631.3	694.2	1,304.8	1,361.1
Depreciation and amortization		383.6	360.8	750.4	710.0
Equity affiliates' income		152.3	143.3	302.9	301.7
Total Assets		38,872.9		38,872.9		39,574.6
Americas | Operating Segments
Segment Reporting Information [Line Items]
Sales		1,287.2	1,245.8	2,574.8	2,497.9
Operating income (loss)		365.7	371.9	753.9	726.3
Depreciation and amortization		178.4	174.1	351.8	343.8
Equity affiliates' income		31.2	44.2	66.3	81.3
Total Assets		11,274.1		11,274.1		12,383.8
Asia | Operating Segments
Segment Reporting Information [Line Items]
Sales		774.1	779.7	1,591.2	1,573.5
Operating income (loss)		191.4	203.6	407.8	414.8
Depreciation and amortization		131.8	116.4	254.7	228.2
Equity affiliates' income		10.5	8.3	20.8	12.5
Total Assets		6,990.9		6,990.9		7,436.5
Europe | Operating Segments
Segment Reporting Information [Line Items]
Sales		727.4	667.9	1,424.6	1,399.1
Operating income (loss)		195.5	201.0	382.0	398.6
Depreciation and amortization		56.8	50.8	111.3	99.0
Equity affiliates' income		27.7	11.7	45.9	32.4
Total Assets		6,215.6		6,215.6		5,849.2
Middle East and India | Operating Segments
Segment Reporting Information [Line Items]
Sales		32.8	35.7	65.6	71.1
Operating income (loss)		(2.9)	5.6	(3.5)	9.5
Depreciation and amortization		6.4	6.7	12.9	13.3
Equity affiliates' income		78.2	73.9	163.2	166.8
Total Assets		10,067.4		10,067.4		8,477.4
Corporate and other | Operating Segments
Segment Reporting Information [Line Items]
Sales		94.7	201.1	191.5	386.0
Operating income (loss)		(118.4)	(87.9)	(235.4)	(188.1)
Depreciation and amortization		10.2	12.8	19.7	25.7
Equity affiliates' income		4.7	$ 5.2	6.7	$ 8.7
Total Assets		$ 4,324.9		$ 4,324.9		$ 5,427.7

[1] Includes balances associated with a consolidated variable interest entity ("VIE"), including amounts reflected in "Total Assets" that can only be used to settle obligations of the VIE of $6,225.5 and $4,393.9 as of 31 March 2025 and 30 September 2024, respectively, as well as liabilities of the VIE reflected within "Total Liabilities" for which creditors do not have recourse to the general credit of Air Products of $4,479.5 and $3,473.4 as of 31 March 2025 and 30 September 2024, respectively. Refer to Note 3, Variable Interest Entities, for additional information regarding the NEOM Green Hydrogen Company joint venture.