Financial Instruments (Effects of Derivatives Not Designated as a Hedging Instrument) (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Income Statement Location [Axis]: us-gaap:OtherNonoperatingIncomeExpense
Derivative Instruments, Gain (Loss) [Line Items]
Total (Gain) Loss Recognized in Income	$ (1.5)	$ 0.1	$ (2.8)	$ (29.7)
Income Statement Location [Axis]: us-gaap:OtherNonoperatingIncomeExpense | Forward exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Total (Gain) Loss Recognized in Income	(2.0)	0.0	(2.2)	(0.8)
Income Statement Location [Axis]: us-gaap:OtherNonoperatingIncomeExpense | De-designated interest rate swap
Derivative Instruments, Gain (Loss) [Line Items]
Total (Gain) Loss Recognized in Income	0.0	0.1	(1.9)	(27.2)
Income Statement Location [Axis]: us-gaap:OtherNonoperatingIncomeExpense | Other
Derivative Instruments, Gain (Loss) [Line Items]
Total (Gain) Loss Recognized in Income	0.5	0.0	1.3	(1.7)
Income Statement Location [Axis]: apd:OtherIncomeExpenseNet
Derivative Instruments, Gain (Loss) [Line Items]
Total (Gain) Loss Recognized in Income	0.4	4.0	0.2	(2.7)
Income Statement Location [Axis]: apd:OtherIncomeExpenseNet | Forward exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Total (Gain) Loss Recognized in Income	0.4	4.0	0.2	(2.7)
Income Statement Location [Axis]: apd:OtherIncomeExpenseNet | De-designated interest rate swap
Derivative Instruments, Gain (Loss) [Line Items]
Total (Gain) Loss Recognized in Income	0.0	0.0	0.0	0.0
Income Statement Location [Axis]: apd:OtherIncomeExpenseNet | Other
Derivative Instruments, Gain (Loss) [Line Items]
Total (Gain) Loss Recognized in Income	$ 0.0	$ 0.0	$ 0.0	$ 0.0