Supplemental Information (Net Sales by Geography) (Details) - USD ($) $ in Millions	12 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016
Net sales:
Net sales	$ 3,248	$ 2,994	$ 3,089
UNITED STATES
Net sales:
Net sales	1,539	1,444	1,491
Europe [Member]
Net sales:
Net sales	864	770	834
Australia [Member]
Net sales:
Net sales	163	151	153
Other Countries [Member]
Net sales:
Net sales	$ 682	$ 629	$ 611