Declaration of Dividend Payable - Additional Information (Detail) - $ / shares		3 Months Ended
	May 11, 2017	Jul. 31, 2017	Jul. 31, 2016
Uncategorized [Abstract]
Cash dividends declared per common share	$ 0.11	$ 0.11	$ 0.11
Cash dividend payable date	Aug. 25, 2017
Cash dividends declared, record date	Aug. 11, 2017