Supplemental Information (Shareholder Activism Costs) (Details) - USD ($) $ in Millions	3 Months Ended
Dec. 31, 2025	Dec. 31, 2024
Disclosure Text Block Supplement [Abstract]
Shareholder activism-related costs	$ 0.0	$ 29.9
Shareholder activism-related costs, net of tax		$ 21.9

Costs incurred in response to a proxy contest for legal, proxy solicitation, executive separation costs, and other professional service fees, net of tax.

No definition available.

Name:	apd_ShareholderActivismCostsNetOfTax
Namespace Prefix:	apd_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration