Earnings per Share (Schedule of Earnings per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Income from continuing operations	$ 430.7	$ 104.2	$ 1,002.7	$ 660.2
Income (Loss) from discontinued operations	43.2	(2.3)	42.2	1,871.5
Net Income Attributable to Air Products	$ 473.9	$ 101.9	$ 1,044.9	$ 2,531.7
Weighted average common shares — Basic	219.5	218.1	219.3	217.9
Employee stock option and other award plans	1.4	1.7	1.4	1.9
Weighted average common shares — Diluted	220.9	219.8	220.7	219.8
Earnings Per Share, Basic [Abstract]
Income from continuing operations (in dollars per share)	$ 1.96	$ 0.48	$ 4.57	$ 3.03
Income (Loss) from discontinued operations (in dollars per share)	0.20	(0.01)	0.19	8.59
Net Income Attributable to Air Products (in dollars per share)	2.16	0.47	4.76	11.62
Earnings Per Share, Diluted [Abstract]
Income from continuing operations (in dollars per share)	1.95	0.47	4.54	3.00
Income (Loss) from discontinued operations (in dollars per share)	0.20	(0.01)	0.19	8.52
Net Income Attributable to Air Products (in dollars per share)	$ 2.15	$ 0.46	$ 4.73	$ 11.52