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, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020		Sep. 30, 2019		Sep. 30, 2018
Earnings Per Share [Abstract]
Net income from continuing operations	$ 486.8	$ 446.5	$ 492.1	$ 475.6	$ 503.2	$ 488.0	$ 421.3	$ 347.5	$ 1,901.0		$ 1,760.0		$ 1,455.6
Net (loss) income from discontinued operations	0.0	0.0	(14.3)	0.0	0.0	0.0	0.0	0.0	(14.3)		0.0		42.2
Net Income Attributable to Air Products	$ 486.8	$ 446.5	$ 477.8	$ 475.6	$ 503.2	$ 488.0	$ 421.3	$ 347.5	$ 1,886.7		$ 1,760.0		$ 1,497.8
Weighted average common shares — Basic	221.3	221.2	221.2	220.9	220.7	220.6	220.2	219.9	221.2		220.3		219.3
Employee stock option and other award plans									1.1		1.3		1.5
Weighted average common shares — Diluted	222.6	222.4	222.3	222.2	222.1	221.9	221.4	221.0	222.3		221.6		220.8
Per Share Data
Basic EPS from continuing operations (in dollars per share)	$ 2.20	$ 2.02	$ 2.22	$ 2.15	$ 2.28	$ 2.21	$ 1.91	$ 1.58	$ 8.59	[1]	$ 7.99	[1]	$ 6.64	[1]
Basic EPS from discontinued operations (in dollars per share)	0	0	(0.06)	0	0	0	0	0	(0.06)	[1]	0	[1]	0.19	[1]
Basic EPS Attributable to Air Products (in dollars per share)	2.20	2.02	2.16	2.15	2.28	2.21	1.91	1.58	8.53	[1]	7.99	[1]	6.83	[1]
Diluted EPS from continuing operations (in dollars per share)	2.19	2.01	2.21	2.14	2.27	2.20	1.90	1.57	8.55	[1]	7.94	[1]	6.59	[1]
Diluted EPS from discontinued operations (in dollars per share)	0	0	(0.06)	0	0	0	0	0	(0.06)	[1]	0	[1]	0.19	[1]
Diluted EPS Attributable to Air Products (in dollars per share)	$ 2.19	$ 2.01	$ 2.15	$ 2.14	$ 2.27	$ 2.20	$ 1.90	$ 1.57	$ 8.49	[1]	$ 7.94	[1]	$ 6.78	[1]

[1] Earnings per share ("EPS") is calculated independently for each component and may not sum to total EPS due to rounding.