Variable Interest Entities (NGHC Joint Venture Project Financing) (Details) - USD ($) $ in Millions	1 Months Ended		12 Months Ended
	Aug. 31, 2023	May 31, 2023	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023	Jun. 30, 2023
Variable Interest Entity [Line Items]
Short-term borrowings			$ 34.7	$ 83.5
Long-term debt, principal amount			17,996.0	14,485.5
Less: Unamortized discount and debt issuance costs			308.9	304.5
Deferred financing fees			3.8	4.6
Operating lease right-of-use assets, net			944.0	1,047.7
Use of cash for payments on operating leases			$ 125.2	154.6	$ 337.8
Variable Interest Entity, Primary Beneficiary | NEOM Green Hydrogen Company
Variable Interest Entity [Line Items]
Voting interest in joint venture			33.33333%
Value of engineering, procurement, and construction agreement		$ 6,700.0
Short-term borrowings			$ 24.0	51.6
Long-term debt			4,677.6	3,053.3
Operating lease right-of-use assets, net			$ 218.0	233.9
Variable Interest Entity, Primary Beneficiary | NEOM Green Hydrogen Company | Land
Variable Interest Entity [Line Items]
Lessee, operating lease, term						50 years
Operating lease right-of-use assets, net						$ 223.0
Use of cash for payments on operating leases	$ 209.0				209.0
Lessee, operating lease, years additional payments due after commencement			30 years
Variable Interest Entity, Primary Beneficiary | NEOM Green Hydrogen Company | De-Designated Interest Rate Swaps
Variable Interest Entity [Line Items]
Gain (loss) on de-designation of cash flow hedges			$ 27.0	(16.3)	0.0
Amount attributable to noncontrolling partners in NGHC			17.6	(10.6)	0.0
Amount attributable to Air Products after tax			7.2	(4.3)	$ 0.0
Variable Interest Entity, Primary Beneficiary | Nonrecourse | NEOM Green Hydrogen Company
Variable Interest Entity [Line Items]
Total principal borrowings			4,900.0	3,300.0
Long-term debt, principal amount			4,909.7	3,271.8
Less: Unamortized discount and debt issuance costs			232.1	218.5
Long-term debt			4,677.6	3,053.3
Variable Interest Entity, Primary Beneficiary | Nonrecourse | NEOM Green Hydrogen Company | Payable in U.S. Dollars
Variable Interest Entity [Line Items]
Long-term debt, principal amount			3,909.6	2,536.6
Variable Interest Entity, Primary Beneficiary | NEOM Green Hydrogen Project Financing, Primary | Nonrecourse | NEOM Green Hydrogen Company
Variable Interest Entity [Line Items]
Project financing, maximum borrowing capacity			$ 6,100.0
Amount of expected debt funding, percent			73.00%
Variable Interest Entity, Primary Beneficiary | NEOM Green Hydrogen Project Financing, Working Capital | Nonrecourse | NEOM Green Hydrogen Company
Variable Interest Entity [Line Items]
Project financing, maximum borrowing capacity			$ 500.0
Variable Interest Entity, Primary Beneficiary | Saudi Riyal Loan Facility Variable-Rate 5.60% | NEOM Green Hydrogen Company
Variable Interest Entity [Line Items]
Short-term borrowings			$ 24.0	$ 51.6
Interest rate, variable percentage			6.30%
Variable Interest Entity, Primary Beneficiary | U.S. Dollar Variable Rate Facility, 6.17% due 2027-2053 | Nonrecourse | NEOM Green Hydrogen Company
Variable Interest Entity [Line Items]
Interest rate, variable percentage			5.49%
Annual margin			1.31%	0.96%
Variable Interest Entity, Primary Beneficiary | U.S. Dollar Variable Rate Facility, 6.17% due 2027-2053 | Nonrecourse | NEOM Green Hydrogen Company | Payable in U.S. Dollars
Variable Interest Entity [Line Items]
Long-term debt, principal amount			$ 2,911.0	$ 1,945.2
Variable Interest Entity, Primary Beneficiary | U.S. Dollar Variable Rate Facility, 5.82% Due 2027-2041 | Nonrecourse | NEOM Green Hydrogen Company
Variable Interest Entity [Line Items]
Interest rate, variable percentage			5.14%
Variable Interest Entity, Primary Beneficiary | U.S. Dollar Variable Rate Facility, 5.82% Due 2027-2041 | Nonrecourse | NEOM Green Hydrogen Company | Payable in U.S. Dollars
Variable Interest Entity [Line Items]
Long-term debt, principal amount			$ 630.6	345.5
Variable Interest Entity, Primary Beneficiary | U.S. Dollar Loan Facility 5.00% due 2027-2053 | Nonrecourse | NEOM Green Hydrogen Company
Variable Interest Entity [Line Items]
Interest rate			5.00%
Variable Interest Entity, Primary Beneficiary | U.S. Dollar Loan Facility 5.00% due 2027-2053 | Nonrecourse | NEOM Green Hydrogen Company | Payable in U.S. Dollars
Variable Interest Entity [Line Items]
Long-term debt, principal amount			$ 368.0	245.9
Variable Interest Entity, Primary Beneficiary | Saudi Riyal Loan Facility variable-rate 2.00% due 2028 to 2041 | Nonrecourse | NEOM Green Hydrogen Company | Other Currency
Variable Interest Entity [Line Items]
Interest rate, variable percentage			2.00%
Long-term debt, principal amount			$ 1,000.1	$ 735.2