Goodwill and Other Intangible Assets (Details) $ in Millions	6 Months Ended
	Oct. 31, 2016 USD ($)
Goodwill [Roll Forward]
Balance at April 30, 2016	$ 590
Acquisitions (Note 14)	182
Foreign currency translation adjustment	(29)
Balance at October 31, 2016	743
Indefinite-lived Intangible Assets [Roll Forward]
Balance at April 30, 2016	595
Acquisitions (Note 14)	65
Foreign currency translation adjustment	(20)
Balance at October 31, 2016	$ 640