Common Stock (Details)	12 Months Ended
	Apr. 30, 2018 shares
Class of Stock [Line Items]
Treasury Stock, Shares, Retired	67,000,000
Common stock, Class A, voting [Member]
Class of Stock [Line Items]
Treasury Stock, Shares, Retired	0
Common Stock, Class B, nonvoting [Member]
Class of Stock [Line Items]
Treasury Stock, Shares, Retired	67,000,000