Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2018
Statement of Stockholders' Equity [Abstract]
Cash dividends (dollars per share)	$ 0.6806	$ 0.648	$ 1.608
Common Stock, Class B, nonvoting [Member]
Equity, Class of Treasury Stock [Line Items]
Treasury Stock, Shares, Retired			67,000,000