Declaration of Dividend Payable - Additional Information (Detail) - $ / shares		3 Months Ended		9 Months Ended
	Nov. 15, 2016	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2017	Jan. 31, 2016
Uncategorized [Abstract]
Cash dividends declared per common share	$ 0.11	$ 0.11	$ 0.10	$ 0.32	$ 0.30
Cash dividend payable date	Feb. 24, 2017
Cash dividends declared, record date	Feb. 10, 2017