Earnings per Share (Schedule of Earnings per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Income from continuing operations	$ 416.4	$ 304.4	$ 572.0	$ 556.0
Income (Loss) from discontinued operations	0.0	1,825.6	(1.0)	1,873.8
Net Income Attributable to Air Products	$ 416.4	$ 2,130.0	$ 571.0	$ 2,429.8
Weighted average common shares — Basic	219.4	217.9	219.2	217.8
Employee stock option and other award plans	1.4	1.8	1.5	1.8
Weighted average common shares — Diluted	220.8	219.7	220.7	219.6
Earnings Per Share, Basic [Abstract]
Income from continuing operations (in dollars per share)	$ 1.90	$ 1.40	$ 2.61	$ 2.55
Income (Loss) from discontinued operations (in dollars per share)	0	8.38	0	8.61
Net Income (Loss) Attributable to Air Products (in dollars per share)	1.90	9.78	2.61	11.16
Earnings Per Share, Diluted [Abstract]
Income from continuing operations (in dollars per share)	1.89	1.39	2.59	2.53
Income (Loss) from discontinued operations (in dollars per share)	0	8.31	0	8.53
Net Income (Loss) Attributable to Air Products (in dollars per share)	$ 1.89	$ 9.70	$ 2.59	$ 11.06