Stockholders' Equity (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Jan. 31, 2022	Oct. 31, 2021	Jul. 31, 2021	Jan. 31, 2021	Oct. 31, 2020	Jul. 31, 2020	Jan. 31, 2022	Jan. 31, 2021
Beginning balance	$ 2,923	$ 2,683	$ 2,656	$ 2,403	$ 2,150	$ 1,975	$ 2,656	$ 1,975
Net income	259	236	192	219	240	324	687	783
Net other comprehensive income (loss)	(6)	2	8	19	15	24	4	58
Declaration of cash dividends	(659)		(172)	(172)		(167)
Stock-based compensation expense	4	3	4	3	3	3
Stock issued under compensation plans	2	1	5	3	5	10
Loss on issuance of treasury stock issued under compensation plans	(4)	(2)	(10)	(7)	(10)	(19)
Ending balance	2,519	2,923	2,683	2,468	2,403	2,150	2,519	2,468
Additional Paid-in Capital [Member]
Beginning balance	3	2	0	0	0	0	0	0
Stock-based compensation expense	4	3	4	3	3	3
Loss on issuance of treasury stock issued under compensation plans	(4)	(2)	(2)	(3)	(3)	(3)
Ending balance	3	3	2	0	0	0	3	0
Retained Earnings [Member]
Beginning balance	3,491	3,255	3,243	3,082	2,849	2,708	3,243	2,708
Net income	259	236	192	219	240	324
Declaration of cash dividends	(659)		(172)	(172)		(167)
Loss on issuance of treasury stock issued under compensation plans			(8)	(4)	(7)	(16)
Ending balance	3,091	3,491	3,255	3,125	3,082	2,849	3,091	3,125
AOCI Attributable to Parent [Member]
Beginning balance	(412)	(414)	(422)	(508)	(523)	(547)	(422)	(547)
Net other comprehensive income (loss)	(6)	2	8	19	15	24
Ending balance	(418)	(412)	(414)	(489)	(508)	(523)	(418)	(489)
Treasury Stock, Common [Member]
Beginning balance	(231)	(232)	(237)	(243)	(248)	(258)	(237)	(258)
Stock issued under compensation plans	2	1	5	3	5	10
Ending balance	(229)	(231)	(232)	(240)	(243)	(248)	(229)	(240)
Common stock, Class A, voting [Member] | Common Stock [Member]
Beginning balance	25	25	25	25	25	25	25	25
Ending balance	25	25	25	25	25	25	25	25
Common stock, Class B, nonvoting [Member] | Common Stock [Member]
Beginning balance	47	47	47	47	47	47	47	47
Ending balance	$ 47	$ 47	$ 47	$ 47	$ 47	$ 47	$ 47	$ 47