Business Segment Information (Schedule of Segment Reporting Information) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025	Sep. 30, 2025
Segment Reporting Information [Line Items]
Sales		$ 3,171.8	$ 2,916.2	$ 6,274.3	$ 5,847.7
Cost of sales		(2,184.4)	(2,053.9)	(4,291.9)	(4,070.4)
Selling and administrative expense		(227.2)	(222.0)	(455.9)	(464.4)
Operating income (loss)		752.7	(2,328.0)	1,487.2	(1,684.4)
Depreciation and amortization				745.7	750.4
Equity affiliates' income		179.4	145.5	351.6	296.1
Investment in net assets of and advances to equity affiliates		5,409.3		5,409.3		$ 5,366.1
Total assets	[1]	41,644.7		41,644.7		41,059.5
Operating Segments
Segment Reporting Information [Line Items]
Sales		3,171.8	2,916.2	6,274.3	5,847.7
Cost of sales		(2,184.4)	(2,053.9)	(4,291.9)	(4,070.4)
Selling and administrative expense		(227.2)	(222.0)	(455.9)	(464.4)
Other segment items		(7.5)	(9.0)	(17.3)	(8.1)
Operating income (loss)		752.7	631.3	1,509.2	1,304.8
Depreciation and amortization		375.0	383.6	745.7	750.4
Equity affiliates' income		179.4	152.3	351.6	302.9
Expenditures for long-lived assets				2,358.8	4,009.1
Investment in net assets of and advances to equity affiliates		5,409.3		5,409.3		5,366.1
Total assets		41,644.7		41,644.7		41,059.5
Americas | Operating Segments
Segment Reporting Information [Line Items]
Sales		1,383.9	1,287.2	2,725.6	2,574.8
Cost of sales		(959.5)	(873.5)	(1,846.1)	(1,728.6)
Selling and administrative expense		(53.8)	(49.8)	(109.0)	(104.2)
Other segment items		3.3	1.8	7.2	11.9
Operating income (loss)		373.9	365.7	777.7	753.9
Depreciation and amortization		171.7	178.4	343.6	351.8
Equity affiliates' income		55.8	31.2	107.5	66.3
Expenditures for long-lived assets				958.8	1,488.7
Investment in net assets of and advances to equity affiliates		632.2		632.2		555.2
Total assets		12,651.3		12,651.3		12,058.7
Asia | Operating Segments
Segment Reporting Information [Line Items]
Sales		832.6	774.1	1,664.1	1,591.2
Cost of sales		(561.6)	(554.4)	(1,134.8)	(1,126.5)
Selling and administrative expense		(33.0)	(30.0)	(61.0)	(61.5)
Other segment items		2.0	1.7	4.0	4.6
Operating income (loss)		240.0	191.4	472.3	407.8
Depreciation and amortization		116.8	131.8	229.5	254.7
Equity affiliates' income		11.7	10.5	25.5	20.8
Expenditures for long-lived assets				186.5	192.7
Investment in net assets of and advances to equity affiliates		348.1		348.1		331.3
Total assets		6,736.1		6,736.1		6,712.2
Europe | Operating Segments
Segment Reporting Information [Line Items]
Sales		789.0	727.4	1,571.0	1,424.6
Cost of sales		(508.9)	(474.0)	(1,000.6)	(923.4)
Selling and administrative expense		(69.7)	(59.2)	(136.7)	(121.1)
Other segment items		1.2	1.3	1.4	1.9
Operating income (loss)		211.6	195.5	435.1	382.0
Depreciation and amortization		72.5	56.8	142.3	111.3
Equity affiliates' income		31.9	27.7	55.3	45.9
Expenditures for long-lived assets				389.9	545.6
Investment in net assets of and advances to equity affiliates		661.3		661.3		649.9
Total assets		7,118.7		7,118.7		6,916.8
Middle East and India | Operating Segments
Segment Reporting Information [Line Items]
Sales		29.2	32.8	59.5	65.6
Cost of sales		(21.5)	(32.3)	(41.4)	(58.0)
Selling and administrative expense		(4.6)	(6.3)	(9.6)	(14.1)
Other segment items		1.5	2.9	1.9	3.0
Operating income (loss)		4.6	(2.9)	10.4	(3.5)
Depreciation and amortization		6.0	6.4	12.2	12.9
Equity affiliates' income		79.2	78.2	163.7	163.2
Expenditures for long-lived assets				762.4	1,721.5
Investment in net assets of and advances to equity affiliates		3,651.8		3,651.8		3,713.2
Total assets		11,520.1		11,520.1		10,919.4
Corporate and other | Operating Segments
Segment Reporting Information [Line Items]
Sales		137.1	94.7	254.1	191.5
Cost of sales		(132.9)	(119.7)	(269.0)	(233.9)
Selling and administrative expense		(66.1)	(76.7)	(139.6)	(163.5)
Other segment items		(15.5)	(16.7)	(31.8)	(29.5)
Operating income (loss)		(77.4)	(118.4)	(186.3)	(235.4)
Depreciation and amortization		8.0	10.2	18.1	19.7
Equity affiliates' income		0.8	$ 4.7	(0.4)	6.7
Expenditures for long-lived assets				61.2	$ 60.6
Investment in net assets of and advances to equity affiliates		115.9		115.9		116.5
Total assets		$ 3,618.5		$ 3,618.5		$ 4,452.4

[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 $7,896.0 and $7,134.7 as of 31 March 2026 and 30 September 2025, 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 $5,295.6 and $4,937.7 as of 31 March 2026 and 30 September 2025, respectively. Refer to Note 3, Variable Interest Entities, for additional information regarding the NEOM Green Hydrogen Company joint venture.