Interim Financial Statements - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended	9 Months Ended
	Jan. 31, 2015	May. 31, 2015	May. 31, 2015	May. 31, 2014	Oct. 31, 2014	Oct. 31, 2013
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program total cost of repurchased shares			$ 48,451,000	$ 26,293,000
Share Repurchase Program - 2014
Equity, Class of Treasury Stock [Line Items]
Amount authorized for repurchase	$ 75,000,000
Expiration date of share repurchase program			Jun. 30, 2016
Additional amount authorized for repurchase	$ 25,000,000
Stock repurchase program total cost of repurchased shares		$ 1,500,000	$ 48,500,000
Repurchase of common stock, shares		28,363	891,041
Remaining authorized repurchase amount		$ 42,100,000	$ 42,100,000
Maximum | Share Repurchase Program - 2013
Equity, Class of Treasury Stock [Line Items]
Amount authorized for repurchase						$ 50,000,000
Maximum | Share Repurchase Program - 2014
Equity, Class of Treasury Stock [Line Items]
Amount authorized for repurchase					$ 50,000,000