Goodwill and Other Intangible Assets (Details) $ in Millions	9 Months Ended
	Jan. 31, 2017 USD ($)
Goodwill [Roll Forward]
Balance at April 30, 2016	$ 590
Acquisitions (Note 14)	182
Foreign currency translation adjustment	(26)
Balance at January 31, 2017	746
Indefinite-lived Intangible Assets [Roll Forward]
Balance at April 30, 2016	595
Acquisitions (Note 14)	65
Foreign currency translation adjustment	(24)
Balance at January 31, 2017	$ 636