Subsequent Event - Additional Information (Detail) - $ / shares							3 Months Ended				9 Months Ended
	May 24, 2019	May 10, 2019	Feb. 22, 2019	Feb. 13, 2019	Feb. 08, 2019	Nov. 15, 2018	Jan. 31, 2019	[1]	Jan. 31, 2018	[1]	Jan. 31, 2019	[1]	Jan. 31, 2018	[1]
Subsequent Event [Line Items]
Cash dividends declared per common share (in usd per share)						$ 0.11	$ 0.11		$ 0.11		$ 0.33		$ 0.33
Subsequent Event
Subsequent Event [Line Items]
Cash dividends declared per common share (in usd per share)				$ 0.11
Cash dividend payable date	May 24, 2019		Feb. 22, 2019
Cash dividends declared, record date		May 10, 2019			Feb. 08, 2019

[1] (a)Basic per share amounts are the same for Class A and Class B shares. Diluted per share amounts for Class A shares are shown above. Diluted earnings per share for Class B shares under the two-class method are $0.07 and $0.18 for the three months ended January 31, 2019 and 2018, and $0.16 and $0.36 for the nine months ended January 31, 2019 and 2018, respectively. See Note D to the Condensed Consolidated Financial Statements.