Consolidated Comprehensive Income Statements - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net Income	$ 1,931.1	$ 1,809.4	$ 1,532.9
Other Comprehensive Income (Loss), net of tax:
Translation adjustments, net of tax	233.4	(356.2)	(244.6)
Net gain (loss) on derivatives, net of tax	43.5
Net gain (loss) on derivatives, net of tax		(44.1)	45.9
Pension and postretirement benefits, net of tax	(68.2)	(326.2)	179.4
Reclassification adjustments:
Currency translation adjustment	0.0	(2.6)	3.1
Derivatives, net ox tax	(57.7)
Derivatives, net of tax		12.3	(30.4)
Pension and postretirement benefits, net of tax	82.5	63.2	133.1
Total Other Comprehensive Income (Loss)	233.5	(653.6)	86.5
Comprehensive Income	2,164.6	1,155.8	1,619.4
Net Income Attributable to Noncontrolling Interests	44.4	49.4	35.1
Other Comprehensive Loss Attributable to Noncontrolling Interests	(2.0)	(19.9)	(19.0)
Comprehensive Income Attributable to Air Products	$ 2,122.2	$ 1,126.3	$ 1,603.3