Stockholders' Equity (Details) - USD ($) $ in Millions	3 Months Ended
	Jul. 31, 2021	Jul. 31, 2020
Beginning balance	$ 2,656	$ 1,975
Net income	192	324
Net other comprehensive income (loss)	8	24
Declaration of cash dividends	(172)	(167)
Stock-based compensation expense	4	3
Stock issued under compensation plans	5	10
Loss on issuance of treasury stock issued under compensation plans	(10)	(19)
Ending balance	2,683	2,150
Additional Paid-in Capital [Member]
Beginning balance	0	0
Stock-based compensation expense	4	3
Loss on issuance of treasury stock issued under compensation plans	(2)	(3)
Ending balance	2	0
Retained Earnings [Member]
Beginning balance	3,243	2,708
Net income	192	324
Declaration of cash dividends	(172)	(167)
Loss on issuance of treasury stock issued under compensation plans	(8)	(16)
Ending balance	3,255	2,849
AOCI Attributable to Parent [Member]
Beginning balance	(422)	(547)
Net other comprehensive income (loss)	8	24
Ending balance	(414)	(523)
Treasury Stock, Common [Member]
Beginning balance	(237)	(258)
Stock issued under compensation plans	5	10
Ending balance	(232)	(248)
Common stock, Class A, voting [Member] | Common Stock [Member]
Beginning balance	25	25
Ending balance	25	25
Common stock, Class B, nonvoting [Member] | Common Stock [Member]
Beginning balance	47	47
Ending balance	$ 47	$ 47