Common Stock Rollforward of Outstanding Shares (Details) - shares shares in Thousands	12 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017
Class of Stock [Line Items]
Beginning balance	481,001	480,106	494,353
Acquisition of treasury stock	(4,357)	(31)	(14,845)
Stock issued under compensation plans	528	926	598
Ending balance	477,172	481,001	480,106
Common stock, Class A, voting [Member]
Class of Stock [Line Items]
Beginning balance	169,062	169,051	169,060
Acquisition of treasury stock	(145)	(25)	(77)
Stock issued under compensation plans	82	36	68
Ending balance	168,999	169,062	169,051
Common Stock, Class B, nonvoting [Member]
Class of Stock [Line Items]
Beginning balance	311,939	311,055	325,293
Acquisition of treasury stock	(4,212)	(6)	(14,768)
Stock issued under compensation plans	446	890	530
Ending balance	308,173	311,939	311,055