Supplemental Information (Net Sales by Geography) (Details) - USD ($) $ in Millions	12 Months Ended
	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2015
Net sales:
Net sales	$ 2,994	$ 3,089	$ 3,134
UNITED STATES
Net sales:
Net sales	1,444	1,491	1,445
Europe [Member]
Net sales:
Net sales	770	834	847
Australia [Member]
Net sales:
Net sales	151	153	175
Other Countries [Member]
Net sales:
Net sales	$ 629	$ 611	$ 667