Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Income Taxes [Line Items]
Cash paid for taxes (net of cash refunds)			$ 645.2	$ 369.2	$ 383.8
Cash provided by operating activities			$ 0.6	$ 59.6	$ 6.7
U.S. federal statutory tax rate			21.00%	21.00%	21.00%
Deemed repatriation tax obligation after application of foreign tax credits			$ 131.1
Deemed repatriation tax obligation in noncurrent liabilities			$ 109.4	$ 134.6
Deemed repatriation tax obligation in noncurrent liabilities, payment period			3 years
Excess tax benefits from share-based compensation			$ 10.2	18.3	$ 17.0
Business and asset actions			244.6	73.7	0.0
Business and asset actions attributable to Air Products after tax			204.9
Valuation allowance against deferred tax assets			36.0
Income (Loss) from Subsidiaries, Tax Expense (Benefit)			15.9
Deferred tax assets, valuation allowance			153.3	100.1
Federal foreign income tax credits			18.7
Cumulative undistributed earnings			8,000.0
U.S. Income and foreign withholding taxes estimate			749.0
Unrecognized tax benefits that would impact effective tax rate			73.8
Reserves for unrecognized tax benefits decrease due to statute of limitations expiration			10.6	25.5	104.6
Reductions for tax positions of prior years			(6.0)	(15.4)	(8.2)
Reduction caused by changes to income tax rates				(10.6)
Interest and penalties related to unrecognized tax benefits			5.0	1.2	(0.2)
Accrued interest and penalties			26.3	22.6
Discontinued Operations
Income Taxes [Line Items]
Tax benefit related to release of reserves					60.0
Foreign Loss Carryforwards
Income Taxes [Line Items]
Deferred tax assets, valuation allowance			33.6
Foreign Capital Losses
Income Taxes [Line Items]
Deferred tax assets, valuation allowance			49.4
Other Charges from Business and Asset Actions
Income Taxes [Line Items]
Deferred tax assets, valuation allowance			34.7
U.S. Federal
Income Taxes [Line Items]
Tax credit carryforwards			20.9
Foreign
Income Taxes [Line Items]
Tax credit carryforwards			17.7
Indefinite tax credit carryforwards			16.0
Operating loss carryforwards			325.9
Operating loss carryforwards not subject to expiration			128.9
PMD | Discontinued Operations
Income Taxes [Line Items]
Tax benefit related to release of reserves	$ 51.8			14.8	51.8
EfW | Discontinued Operations
Income Taxes [Line Items]
Tax benefit related to release of reserves		$ 8.2			8.2
Discontinued operations | PMD
Income Taxes [Line Items]
Reserves for unrecognized tax benefits decrease due to statute of limitations expiration			$ 5.2	17.2	65.6
Related deferred tax assets				$ 2.4	13.8
Discontinued operations | EfW
Income Taxes [Line Items]
Reserves for unrecognized tax benefits decrease due to statute of limitations expiration					8.2
Other reserves
Income Taxes [Line Items]
Tax benefit					21.5
Reserves for unrecognized tax benefits decrease due to statute of limitations expiration					27.5
Related deferred tax assets					$ 8.4