Equity (Changes in Equity) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	$ 7,213.4	$ 7,381.1
Net income	306.4	372.0
Other comprehensive loss	(238.0)	(82.7)
Dividends on common stock (per share $0.86, $0.81)	(187.1)	(174.7)
Dividends to noncontrolling interests	(4.2)	(8.5)
Share-based compensation	9.0	8.3
Treasury shares for stock option and award plans	(0.3)	(2.0)
Tax benefit of stock option and award plans		4.9
Spin-off of Versum	152.6
Cumulative change in accounting principle	8.8
Other equity transactions	0.5	0.6
Balance, end of period	$ 7,261.1	$ 7,499.0
Dividends per share	$ 0.86	$ 0.81
Air Products Shareholders' Equity [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	$ 7,079.6	$ 7,249.0
Net income	299.8	363.6
Other comprehensive loss	(234.9)	(82.7)
Dividends on common stock (per share $0.86, $0.81)	(187.1)	(174.7)
Share-based compensation	9.0	8.3
Treasury shares for stock option and award plans	(0.3)	(2.0)
Tax benefit of stock option and award plans		4.9
Spin-off of Versum	186.5
Cumulative change in accounting principle	8.8
Other equity transactions	0.1	0.7
Balance, end of period	7,161.5	7,367.1
Noncontrolling Interest [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	133.8	132.1
Net income	6.6	8.4
Other comprehensive loss	(3.1)
Dividends to noncontrolling interests	(4.2)	(8.5)
Spin-off of Versum	(33.9)
Other equity transactions	0.4	(0.1)
Balance, end of period	$ 99.6	$ 131.9