Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2019
Earnings Per Share [Abstract]
Net income available to common stockholders	$ 903	$ 827	$ 835
Share data (in thousands):
Basic average common shares outstanding (shares)	478,527	477,765	478,956
Dilutive effect of stock-based awards (shares)	2,150	2,644	3,111
Diluted average common shares outstanding (shares)	480,677	480,409	482,067
Basic earnings per share (dollars per share)	$ 1.89	$ 1.73	$ 1.74
Diluted earnings per share (dollars per share)	$ 1.88	$ 1.72	$ 1.73
Antidilutive common stock-based awards excluded from calculation of diluted earnings per share (shares)	234	301	447