Earnings per Share (Schedule of Earnings per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended									12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017		Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017		Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share [Abstract]
Income from continuing operations	$ 474.2	$ 104.2	$ 304.4		$ 251.6	$ 289.4	$ 250.3	$ 278.9	$ 280.9	$ 1,134.4		$ 1,099.5	$ 933.3
Income (Loss) from discontinued operations	(5.5)	(2.3)	1,825.6	[1]	48.2	104.6	96.5	(752.2)	82.7	1,866.0	[1]	(468.4)	344.6
Net Income Attributable to Air Products	$ 468.7	$ 101.9	$ 2,130.0		$ 299.8	$ 394.0	$ 346.8	$ (473.3)	$ 363.6	$ 3,000.4		$ 631.1	$ 1,277.9
Weighted average common shares — Basic										218.0		216.4	214.9
Employee stock option and other award plans										1.8		1.9	2.4
Weighted average common shares — Diluted										219.8		218.3	217.3
Basic Earnings Per Common Share Attributable to Air Products
Income from continuing operations (in dollars per share)	$ 2.17	$ 0.48	$ 1.40		$ 1.16	$ 1.33	$ 1.16	$ 1.29	$ 1.30	$ 5.20		$ 5.08	$ 4.34
Income (Loss) from discontinued operations (in dollars per share)	(0.02)	(0.01)	8.38		0.22	0.48	0.44	(3.48)	0.38	8.56		(2.16)	1.61
Net Income Attributable to Air Products (in dollars per share)	2.15	0.47	9.78		1.38	1.81	1.60	(2.19)	1.68	13.76		2.92	5.95
Diluted Earnings Per Common Share Attributable to Air Products
Income from continuing operations (in dollars per share)	2.15	0.47	1.39		1.15	1.32	1.15	1.28	1.29	5.16		5.04	4.29
Income (Loss) from discontinued operations (in dollars per share)	(0.02)	(0.01)	8.31		0.22	0.48	0.44	(3.45)	0.38	8.49		(2.15)	1.59
Net Income Attributable to Air Products (in dollars per share)	$ 2.13	$ 0.46	$ 9.70		$ 1.37	$ 1.80	$ 1.59	$ (2.17)	$ 1.67	$ 13.65		$ 2.89	$ 5.88

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