Share-Based Compensation (Summary of Stock Option Activity) (Details) shares in Thousands	12 Months Ended
	Sep. 30, 2017 $ / shares shares
Shares
Outstanding, beginning (shares) | shares	3,916
Equitable adjustment upon separation (shares) | shares	277	[1]
Surrender upon separation (shares) | shares	(102)	[2]
Exercised (shares) | shares	(886)
Forfeited (shares) | shares	(3)
Outstanding, ending (shares) | shares	3,202
Exercisable (shares) | shares	3,149
Weighted Average Exercise Price
Outstanding, beginning (in dollars per share) | $ / shares	$ 90.28
Equitable adjustment upon separation (in dollars per share) | $ / shares	0.00	[1]
Surrender upon separation (in dollars per share) | $ / shares	97.63	[2]
Exercised (in dollars per share) | $ / shares	80.76
Forfeited (in dollars per share) | $ / shares	105.28
Outstanding, ending (in dollars per share) | $ / shares	84.85
Exercisable (in dollars per share) | $ / shares	$ 84.00

[1] Applicable deferred stock units have been adjusted by the conversion ratio of 1.071 to preserve the intrinsic value immediately before and after the spin-off of Versum.

[2] In connection with the spin-off of Versum, EMD employees surrendered their outstanding Air Products equity awards, which were converted into Versum equity awards of equivalent fair value.