Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020
Basic and diluted earnings per share
Net income available to common stockholders	$ 219	$ 231	$ 783	$ 699
Share data (in thousands):
Basic average common shares outstanding	478,599	477,898	478,471	477,643
Dilutive effect of stock-based awards	2,237	2,859	2,194	2,793
Diluted average common shares outstanding	480,836	480,757	480,665	480,436
Basic earnings per share (dollars per share)	$ 0.46	$ 0.48	$ 1.64	$ 1.46
Diluted earnings per share (dollars per share)	$ 0.45	$ 0.48	$ 1.63	$ 1.45