Common Stock Rollforward of Outstanding Shares (Details) - shares shares in Thousands	12 Months Ended
	Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2019
Class of Stock [Line Items]
Beginning balance	478,209	477,172	481,001
Acquisition of treasury stock	0	(16)	(4,357)
Stock issued under compensation plans	520	1,053	528
Ending balance	478,729	478,209	477,172
Common stock, Class A, voting [Member]
Class of Stock [Line Items]
Beginning balance	169,040	168,999	169,062
Acquisition of treasury stock	0	(13)	(145)
Stock issued under compensation plans	70	54	82
Ending balance	169,110	169,040	168,999
Common Stock, Class B, nonvoting [Member]
Class of Stock [Line Items]
Beginning balance	309,169	308,173	311,939
Acquisition of treasury stock	0	(3)	(4,212)
Stock issued under compensation plans	450	999	446
Ending balance	309,619	309,169	308,173