Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Oct. 31, 2021	Oct. 31, 2020	Oct. 31, 2021	Oct. 31, 2020
Basic and diluted earnings per share
Net income available to common stockholders	$ 236	$ 240	$ 428	$ 564
Share data (in thousands):
Basic average common shares outstanding	478,857	478,506	478,822	478,413
Dilutive effect of stock-based awards	1,661	2,242	1,793	2,172
Diluted average common shares outstanding	480,518	480,748	480,615	480,585
Basic earnings per share (dollars per share)	$ 0.49	$ 0.50	$ 0.89	$ 1.18
Diluted earnings per share (dollars per share)	$ 0.49	$ 0.50	$ 0.89	$ 1.17