Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions		Total	Common Stock [Member] Common stock, Class A, voting [Member]	Common Stock [Member] Common Stock, Class B, nonvoting [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Treasury Stock, Common [Member]
Beginning Balance at Apr. 30, 2017		$ 1,370	$ 25	$ 43	$ 65	$ 4,470	$ (390)	$ (2,843)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Retirement of treasury stock (Note 8)	[1]	0		(10)	(8)	(2,684)		2,702
Stock split (Note 8)	[2]	0		14	(14)
Net income		717				717
Net other comprehensive income (loss)		12					12
Cash dividends		(773)				(773)
Acquisition of treasury stock		(1)						(1)
Stock-based compensation expense		19			19
Stock issued under compensation plans		30						30
Loss on issuance of treasury stock issued under compensation plans		(58)			(58)
Ending Balance at Apr. 30, 2018		1,316	25	47	4	1,730	(378)	(112)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		835				835
Net other comprehensive income (loss)		15					15
Cash dividends		(310)				(310)
Acquisition of treasury stock		(207)						(207)
Stock-based compensation expense		14			14
Stock issued under compensation plans		19						19
Loss on issuance of treasury stock issued under compensation plans		(30)			(18)	(12)
Other		(5)				(5)
Ending Balance at Apr. 30, 2019		1,647	25	47	0	2,238	(363)	(300)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		827				827
Net other comprehensive income (loss)		(141)					(141)
Cash dividends		(325)				(325)
Acquisition of treasury stock		(1)						(1)
Stock-based compensation expense		11			11
Stock issued under compensation plans		43						43
Loss on issuance of treasury stock issued under compensation plans		(86)			(11)	(75)
Ending Balance at Apr. 30, 2020		$ 1,975	$ 25	$ 47	$ 0	$ 2,708	$ (547)	$ (258)

[1] Retirement of 67 million shares of Class B common stock previously held as treasury shares.

[2] Stock split effected in the form of a stock dividend of one share of Class B common stock for every four shares of either Class A or Class B common stock.