Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Income Taxes [Line Items]
Cash paid for taxes (net of cash refunds)		$ 615.9	$ 645.2	$ 369.2
Cash provided by operating activities		0.0	$ 0.6	$ 59.6
Income tax paid, tax credit		$ 50.0
U.S. federal statutory tax rate		21.00%	21.00%	21.00%
Deemed repatriation tax obligation after application of foreign tax credits	$ 101.8	$ 101.8
Deemed repatriation tax obligation in noncurrent liabilities	60.8	$ 60.8	$ 109.4
Deemed repatriation tax obligation in noncurrent liabilities, payment period		2 years
Gain on sale of business	1,575.6	$ 1,575.6	0.0	$ 0.0
Excess tax benefits from share-based compensation		3.6	10.2	18.3
Business and asset actions		57.0	244.6	73.7
Business and asset actions attributable to Air Products after tax		43.8	204.9	61.0
Valuation allowance against deferred tax assets	36.0	36.0
Income (Loss) from Subsidiaries, Tax Expense (Benefit)			15.9
Deferred tax assets, valuation allowance	158.4	158.4	153.3
Federal foreign income tax credits	18.2	18.2
Cumulative undistributed earnings	9,200.0	9,200.0
U.S. Income and foreign withholding taxes estimate	845.3	845.3
Unrecognized tax benefits that would impact effective tax rate	80.3	80.3
Reserves for unrecognized tax benefits decrease due to statute of limitations expiration		9.9	10.6	25.5
Reductions for tax positions of prior years		(0.3)	(6.0)	(15.4)
Reduction caused by changes to income tax rates				(10.6)
Interest and penalties related to unrecognized tax benefits		1.8	5.0	1.2
Accrued interest and penalties	28.5	28.5	26.3
Foreign Loss Carryforwards
Income Taxes [Line Items]
Deferred tax assets, valuation allowance	43.8	43.8
Foreign Capital Losses
Income Taxes [Line Items]
Deferred tax assets, valuation allowance	53.5	53.5
Other Charges from Business and Asset Actions
Income Taxes [Line Items]
Deferred tax assets, valuation allowance	39.9	39.9
U.S. Federal
Income Taxes [Line Items]
Tax credit carryforwards	19.7	19.7
Foreign
Income Taxes [Line Items]
Tax credit carryforwards	18.1	18.1
Indefinite tax credit carryforwards	18.0	18.0
Operating loss carryforwards	347.3	347.3
Operating loss carryforwards not subject to expiration	$ 99.7	$ 99.7
PMD | Discontinued Operations
Income Taxes [Line Items]
Tax benefit related to release of reserves				14.8
Discontinued operations | PMD
Income Taxes [Line Items]
Reserves for unrecognized tax benefits decrease due to statute of limitations expiration			$ 5.2	17.2
Related deferred tax assets				$ 2.4