Consolidated Comprehensive Income Statements - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017		Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net Income	$ 1,532.9	$ 3,021.2	[1]	$ 661.5
Other Comprehensive Income (Loss), net of tax:
Translation adjustments, net of tax	(244.6)	101.9		9.9
Net gain (loss) on derivatives, net of tax	45.9	(12.6)		13.7
Pension and postretirement benefits, net of tax	179.4	251.6		(335.1)
Reclassification adjustments:
Currency translation adjustment	3.1	57.3		2.7
Derivatives, net of tax	(30.4)	24.2		(36.0)
Pension and postretirement benefits, net of tax	133.1	110.7		87.2
Total Other Comprehensive Income (Loss)	86.5	533.1		(257.6)
Comprehensive Income	1,619.4	3,554.3		403.9
Net Income Attributable to Noncontrolling Interests	35.1	20.8		30.4
Other Comprehensive Income (Loss) Attributable to Noncontrolling Interests	(19.0)	3.7		4.8
Comprehensive Income Attributable to Air Products	$ 1,603.3	$ 3,529.8		$ 368.7

[1] Includes the after-tax gain on the sale of PMD. For additional information, see Note 3, Discontinued Operations.