Earnings per Share (Schedule of Earnings per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Income from continuing operations	$ 155.6	$ 251.6
Income (Loss) from discontinued operations	(1.0)	48.2
Net Income Attributable to Air Products	$ 154.6	$ 299.8
Weighted average common shares — Basic	218.9	217.7
Employee stock option and other award plans	1.5	2.0
Weighted average common shares — Diluted	220.4	219.7
Earnings Per Share, Basic [Abstract]
Income from continuing operations (in dollars per share)	$ 0.71	$ 1.16
Income (Loss) from discontinued operations (in dollars per share)	0	0.22
Net Income (Loss) Attributable to Air Products (in dollars per share)	0.71	1.38
Earnings Per Share, Diluted [Abstract]
Income from continuing operations (in dollars per share)	0.70	1.15
Income (Loss) from discontinued operations (in dollars per share)	0	0.22
Net Income (Loss) Attributable to Air Products (in dollars per share)	$ 0.70	$ 1.37