Supplemental Information (Net Sales by Geography) (Details) - USD ($) $ in Millions	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2018
Geographic Areas, Revenues from External Customers [Abstract]
Net sales	$ 3,363	$ 3,324	$ 3,248
United States
Geographic Areas, Revenues from External Customers [Abstract]
Net sales	1,690	1,563	1,529
United Kingdom
Geographic Areas, Revenues from External Customers [Abstract]
Net sales	180	199	206
Germany
Geographic Areas, Revenues from External Customers [Abstract]
Net sales	171	159	146
Australia
Geographic Areas, Revenues from External Customers [Abstract]
Net sales	155	164	163
Mexico
Geographic Areas, Revenues from External Customers [Abstract]
Net sales	155	166	162
Other Countries
Geographic Areas, Revenues from External Customers [Abstract]
Net sales	$ 1,012	$ 1,073	$ 1,042