Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended
	Jul. 31, 2020	Jul. 31, 2019
Basic and diluted earnings per share
Net income available to common stockholders	$ 324	$ 186
Share data (in thousands):
Basic average common shares outstanding	478,327	477,369
Dilutive effect of stock-based awards	2,102	2,719
Diluted average common shares outstanding	480,429	480,088
Basic earnings per share (dollars per share)	$ 0.68	$ 0.39
Diluted earnings per share (dollars per share)	$ 0.67	$ 0.39