Subsequent Event - Additional Information (Detail) (USD $)	0 Months Ended	3 Months Ended		6 Months Ended		0 Months Ended
	Aug. 20, 2014	Oct. 31, 2014	Oct. 31, 2013	Oct. 31, 2014	Oct. 31, 2013	Nov. 19, 2014 Class A Common Shares Subsequent Event	Nov. 19, 2014 Class B Common Shares Subsequent Event
Subsequent Event [Line Items]
Cash dividends declared per common share	$ 0.10	$ 0.10	$ 0.10	$ 0.20	$ 0.10	$ 0.10	$ 0.10
Cash dividend payable date	Dec. 05, 2014					Feb. 24, 2015	Feb. 24, 2015
Cash dividends declared, record date	Nov. 14, 2014					Feb. 06, 2015	Feb. 06, 2015