Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Basic and diluted earnings per share
Net income available to common stockholders	$ 240	$ 282	$ 564	$ 468
Share data (in thousands):
Basic average common shares outstanding	478,506	477,680	478,413	477,522
Dilutive effect of stock-based awards	2,242	2,801	2,172	2,760
Diluted average common shares outstanding	480,748	480,481	480,585	480,282
Basic earnings per share (dollars per share)	$ 0.50	$ 0.59	$ 1.18	$ 0.98
Diluted earnings per share (dollars per share)	$ 0.50	$ 0.59	$ 1.17	$ 0.97