Consolidated Statements of Equity - USD ($) $ in Millions	Total	Cumulative change in accounting principle	Common Stock	Capital in Excess of Par Value	Retained Earnings	Retained Earnings Cumulative change in accounting principle	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Air Products Shareholders’ Equity	Air Products Shareholders’ Equity Cumulative change in accounting principle	Non-controlling Interests
Beginning balance at Sep. 30, 2018	$ 11,176.3	$ (17.1)	$ 249.4	$ 1,029.3	$ 13,409.9	$ (17.1)	$ (1,741.9)	$ (2,089.2)	$ 10,857.5	$ (17.1)	$ 318.8
Stockholders' Equity [Roll Forward]
Net income	1,809.4				1,760.0				1,760.0		49.4
Other comprehensive income (loss)	(653.6)						(633.7)		(633.7)		(19.9)
Dividends on common stock	(1,008.3)				(1,008.3)				(1,008.3)
Dividends to noncontrolling interests	(12.2)										(12.2)
Share-based compensation	40.7			40.7					40.7
Issuance of treasury shares for stock option and award plans	61.9			2.2				59.7	61.9
Other equity transactions	(8.8)			(1.3)	(6.1)				(7.4)		(1.4)
Ending balance at Sep. 30, 2019	11,388.3		249.4	1,070.9	14,138.4		(2,375.6)	(2,029.5)	11,053.6		334.7
Stockholders' Equity [Roll Forward]
Net income	1,931.1				1,886.7				1,886.7		44.4
Other comprehensive income (loss)	233.5						235.5		235.5		(2.0)
Dividends on common stock	(1,144.1)				(1,144.1)				(1,144.1)
Dividends to noncontrolling interests	(31.8)										(31.8)
Share-based compensation	44.2			44.2					44.2
Issuance of treasury shares for stock option and award plans	15.4			(14.1)				29.5	15.4
Investments by noncontrolling interests	17.1										17.1
Other equity transactions	(10.6)			(6.2)	(5.3)				(11.5)		(0.9)
Ending balance at Sep. 30, 2020	12,443.1		249.4	1,094.8	14,875.7		(2,140.1)	(2,000.0)	12,079.8		363.3
Stockholders' Equity [Roll Forward]
Net income	2,114.9				2,099.1				2,099.1		15.8
Other comprehensive income (loss)	663.0						624.2		624.2		38.8
Dividends on common stock	(1,292.6)				(1,292.6)				(1,292.6)
Dividends to noncontrolling interests	(5.3)										(5.3)
Share-based compensation	43.5			43.5					43.5
Issuance of treasury shares for stock option and award plans	(9.4)			(21.5)				12.1	(9.4)
Investments by noncontrolling interests	139.8										139.8
Purchase of noncontrolling interests	(5.3)			(1.2)					(1.2)		(4.1)
Other equity transactions	(3.7)			0.2	(3.9)				(3.7)		0.0
Ending balance at Sep. 30, 2021	$ 14,088.0		$ 249.4	$ 1,115.8	$ 15,678.3	$ 1.3	$ (1,515.9)	$ (1,987.9)	$ 13,539.7		$ 548.3