Supplemental Information (Net Sales by Geography) (Details) - USD ($) $ in Millions	12 Months Ended
	Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2019
Geographic Areas, Revenues from External Customers [Abstract]
Net sales	$ 3,461	$ 3,363	$ 3,324
United States
Geographic Areas, Revenues from External Customers [Abstract]
Net sales	1,748	1,690	1,563
Australia
Geographic Areas, Revenues from External Customers [Abstract]
Net sales	209	155	164
Germany
Geographic Areas, Revenues from External Customers [Abstract]
Net sales	206	171	159
United Kingdom
Geographic Areas, Revenues from External Customers [Abstract]
Net sales	205	180	199
Mexico
Geographic Areas, Revenues from External Customers [Abstract]
Net sales	150	155	166
Other Countries
Geographic Areas, Revenues from External Customers [Abstract]
Net sales	$ 943	$ 1,012	$ 1,073