Stockholders' Equity Common Stock (Details) - shares		9 Months Ended
	May 24, 2017	Jan. 31, 2018
Class of Stock [Line Items]
Balance at April 30, 2017		454,627,000
Retirement of treasury stock		(67,000,000)
Stock split		96,905,000
Balance at January 31, 2018		484,532,000
Common stock, Class A, voting [Member]
Class of Stock [Line Items]
Balance at April 30, 2017		170,000,000
Retirement of treasury stock		0
Stock split		0
Balance at January 31, 2018		170,000,000
Common stock, Class B, nonvoting [Member]
Class of Stock [Line Items]
Balance at April 30, 2017		284,627,000
Retirement of treasury stock	(67,000,000)	(67,000,000)
Stock split		96,905,000
Balance at January 31, 2018		314,532,000