Business Segment Information (Schedule of Segment Reporting Information) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023	Sep. 30, 2023
Segment Reporting Information [Line Items]
Sales		$ 2,930.2	$ 3,200.1	$ 5,927.6	$ 6,374.8
Operating income (loss)		637.2	459.8	1,304.1	1,111.8
Depreciation and amortization				710.0	661.1
Equity affiliates' income		143.3	165.9	301.7	275.9
Total Assets	[1]	35,921.7		35,921.7		$ 32,002.5
Operating Segments
Segment Reporting Information [Line Items]
Sales		2,930.2	3,200.1	5,927.6	6,374.8
Operating income (loss)		694.2	645.4	1,361.1	1,297.4
Depreciation and amortization		360.8	339.6	710.0	661.1
Equity affiliates' income		143.3	165.9	301.7	275.9
Total Assets		35,921.7		35,921.7		32,002.5
Americas | Operating Segments
Segment Reporting Information [Line Items]
Sales		1,245.8	1,373.1	2,497.9	2,757.3
Operating income (loss)		371.9	324.2	726.3	667.2
Depreciation and amortization		174.1	161.7	343.8	317.7
Equity affiliates' income		44.2	28.1	81.3	44.5
Total Assets		11,372.6		11,372.6		9,927.5
Asia | Operating Segments
Segment Reporting Information [Line Items]
Sales		779.7	813.9	1,573.5	1,591.7
Operating income (loss)		203.6	233.0	414.8	468.9
Depreciation and amortization		116.4	110.0	228.2	211.9
Equity affiliates' income		8.3	7.3	12.5	14.7
Total Assets		7,203.3		7,203.3		7,009.6
Europe | Operating Segments
Segment Reporting Information [Line Items]
Sales		667.9	752.9	1,399.1	1,544.8
Operating income (loss)		201.0	173.2	398.6	319.0
Depreciation and amortization		50.8	48.3	99.0	92.6
Equity affiliates' income		11.7	29.5	32.4	47.2
Total Assets		5,113.2		5,113.2		4,649.8
Middle East and India | Operating Segments
Segment Reporting Information [Line Items]
Sales		35.7	44.8	71.1	86.2
Operating income (loss)		5.6	1.3	9.5	8.0
Depreciation and amortization		6.7	6.6	13.3	13.2
Equity affiliates' income		73.9	98.9	166.8	163.0
Total Assets		6,835.9		6,835.9		5,708.4
Corporate and other | Operating Segments
Segment Reporting Information [Line Items]
Sales		201.1	215.4	386.0	394.8
Operating income (loss)		(87.9)	(86.3)	(188.1)	(165.7)
Depreciation and amortization		12.8	13.0	25.7	25.7
Equity affiliates' income		5.2	$ 2.1	8.7	$ 6.5
Total Assets		$ 5,396.7		$ 5,396.7		$ 4,707.2

[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 $3,178.7 and $2,256.8 as of 31 March 2024 and 30 September 2023, 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 $2,499.0 and $1,461.1 as of 31 March 2024 and 30 September 2023, respectively. Refer to Note 3, Variable Interest Entities, for additional information regarding the NEOM Green Hydrogen Company joint venture.