Declaration of Dividend Payable - Additional Information (Detail) - $ / shares		3 Months Ended		6 Months Ended
	Aug. 22, 2018	Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2018	Oct. 31, 2017
Dividends [Abstract]
Cash dividends declared per common share	$ 0.11	$ 0.11	$ 0.11	$ 0.22	$ 0.22
Cash dividend payable date				Dec. 05, 2018
Cash dividends declared, record date				Nov. 19, 2018
Cash dividends payable, declared date				Aug. 22, 2018