Equity (Changes in Equity) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Balance, beginning of period		$ 7,499.0	$ 7,503.3	$ 7,381.1	$ 7,521.4
Net income		(465.5)	296.9	(93.5)	629.0
Other comprehensive income (loss)		164.7	(190.9)	82.0	(424.7)
Dividends on common stock		(185.8)	(173.9)	(360.5)	(339.3)
Dividends to noncontrolling interests		(6.3)	(13.1)	(14.8)	(19.3)
Share-based compensation expense		9.3	12.9	19.5	24.8
Treasury shares for stock option and award plans		32.8	32.8	30.8	62.9
Tax benefit of stock option and award plans		4.8	9.4	9.7	22.9
Other		0.1	(1.1)	(1.2)	(1.4)
Balance, end of period		7,053.1	7,476.3	7,053.1	7,476.3
Net income related to redeemable noncontrolling interests		0.0	0.0	0.0	5.4
Air Products Shareholders' Equity [Member]
Balance, beginning of period		7,367.1	7,351.5	7,249.0	7,365.8
Net income		(473.3)	290.0	(109.7)	614.6
Other comprehensive income (loss)		161.9	(191.5)	79.2	(420.2)
Dividends on common stock		(185.8)	(173.9)	(360.5)	(339.3)
Dividends to noncontrolling interests		0.0	0.0	0.0	0.0
Share-based compensation expense		9.3	12.9	19.5	24.8
Treasury shares for stock option and award plans		32.8	32.8	30.8	62.9
Tax benefit of stock option and award plans		4.8	9.4	9.7	22.9
Other		(0.2)	1.3	(1.4)	1.0
Balance, end of period		6,916.6	7,332.5	6,916.6	7,332.5
Noncontrolling Interests [Member]
Balance, beginning of period		131.9	151.8	132.1	155.6
Net income	[1]	7.8	6.9	16.2	14.4
Other comprehensive income (loss)		2.8	0.6	2.8	(4.5)
Dividends on common stock		0.0	0.0	0.0	0.0
Dividends to noncontrolling interests		(6.3)	(13.1)	(14.8)	(19.3)
Share-based compensation expense		0.0	0.0	0.0	0.0
Treasury shares for stock option and award plans		0.0	0.0	0.0	0.0
Tax benefit of stock option and award plans		0.0	0.0	0.0	0.0
Other		0.3	(2.4)	0.2	(2.4)
Balance, end of period		$ 136.5	$ 143.8	$ 136.5	$ 143.8

[1] Net income attributable to noncontrolling interests for the three and six months ended 31 March 2015 excludes net income of $0.0 and $5.4, respectively, related to redeemable noncontrolling interests, which were not part of total equity. There was no net income related to redeemable noncontrolling interests for the three and six months ended 31 March 2016.