Common Stock Rollforward of Outstanding Shares (Details) - shares shares in Thousands	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2018
Class of Stock [Line Items]
Beginning balance	477,172	481,001	480,106
Acquisition of treasury stock	(16)	(4,357)	(31)
Stock issued under compensation plans	1,053	528	926
Ending balance	478,209	477,172	481,001
Common stock, Class A, voting [Member]
Class of Stock [Line Items]
Beginning balance	168,999	169,062	169,051
Acquisition of treasury stock	(13)	(145)	(25)
Stock issued under compensation plans	54	82	36
Ending balance	169,040	168,999	169,062
Common Stock, Class B, nonvoting [Member]
Class of Stock [Line Items]
Beginning balance	308,173	311,939	311,055
Acquisition of treasury stock	(3)	(4,212)	(6)
Stock issued under compensation plans	999	446	890
Ending balance	309,169	308,173	311,939