Variable Interest Entities - Balance Sheet Accounts (Details) - USD ($) $ in Millions		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Assets
Cash and cash items		$ 1,617.0	$ 2,711.0
Trade receivables, net		1,700.4	1,794.4
Prepaid expenses		177.0	156.8
Other receivables and current assets		722.1	515.8
Total current assets		5,200.5	6,282.9
Plant and equipment, net		17,472.1	14,160.5	$ 13,254.6
Operating lease right-of-use assets, net		974.0	694.8
Other noncurrent assets		1,229.9	947.0
Total noncurrent assets		26,802.0	20,909.7
Total assets	[1]	32,002.5	27,192.6
Liabilities [Abstract]
Accounts Payable and Accrued Liabilities, Current		2,890.1	2,771.6
Accrued income taxes		131.2	135.2
Total current liabilities		3,895.8	3,465.8
Noncurrent operating lease liabilities		631.1	592.1
Other noncurrent liabilities		1,118.0	1,099.1
Deferred income taxes		1,266.0	1,247.4
Total noncurrent liabilities		12,446.4	10,024.4
Total liabilities	[1]	16,342.2	13,490.2
Equity [Abstract]
Accumulated other comprehensive loss		(2,449.4)	(2,786.1)
Noncontrolling interests	[1]	1,347.4	558.4
Nonrelated Party
Liabilities [Abstract]
Long-term Debt		9,280.6	6,433.8
Related Party
Assets
Trade receivables, net		80.0	55.0
Liabilities [Abstract]
Long-term Debt		150.7	652.0
Variable Interest Entity, Primary Beneficiary | NEOM Green Hydrogen Company
Assets
Cash and cash items		78.2	274.7
Trade receivables, net		0.0	1.3
Prepaid expenses		21.4	0.1
Other receivables and current assets		181.6	23.3
Total current assets		281.2	299.4
Plant and equipment, net		1,396.1	218.8
Operating lease right-of-use assets, net		228.9	0.0
Other noncurrent assets		350.6	1.5
Total noncurrent assets		1,975.6	220.3
Total assets		2,256.8	519.7
Liabilities [Abstract]
Accounts Payable and Accrued Liabilities, Current		141.0	58.1
Accrued income taxes		0.6	0.0
Total current liabilities		141.6	58.1
Noncurrent operating lease liabilities		18.9	0.0
Other noncurrent liabilities		2.1	1.4
Deferred income taxes		24.1	0.0
Total noncurrent liabilities		1,319.5	448.7
Total liabilities		1,461.1	506.8
Equity [Abstract]
Accumulated other comprehensive loss		77.7	0.0
Noncontrolling interests		723.6	30.0
Variable Interest Entity, Primary Beneficiary | NEOM Green Hydrogen Company | Nonrelated Party
Liabilities [Abstract]
Long-term Debt		1,274.4	0.0
Variable Interest Entity, Primary Beneficiary | NEOM Green Hydrogen Company | Related Party
Liabilities [Abstract]
Long-term Debt		$ 0.0	$ 447.3

[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 $2,256.8 and $519.7 as of 30 September 2023 and 30 September 2022, 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 $1,461.1 and $506.8 as of 30 September 2023 and 30 September 2022, respectively. Refer to Note 3, Variable Interest Entities, for additional information.