Repurchase of Common Stock - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Nov. 30, 2013	May. 31, 2015	May. 31, 2014	Jun. 23, 2014	Oct. 01, 2013
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount					$ 25,000,000
Stock repurchased and retired during period, shares	369,900	546,977
Stock repurchased and retired during period, value	$ 13,300,000	$ 21,100,000
Remaining stock available to repurchase		$ 15,500,000
Prior Periods
Equity, Class of Treasury Stock [Line Items]
Stock repurchased and retired during period, shares			89,569
Stock repurchased and retired during period, value			$ 1,300,000
Maximum [Member]
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount				$ 50,000,000
Common Stock
Equity, Class of Treasury Stock [Line Items]
Stock repurchased and retired during period, shares			(459,000)
Stock repurchased and retired during period, value			$ 138,000
Additional Paid-in Capital
Equity, Class of Treasury Stock [Line Items]
Stock repurchased and retired during period, value			2,232,000
Retained Earnings
Equity, Class of Treasury Stock [Line Items]
Stock repurchased and retired during period, value			12,308,000
Share Repurchase Plan | Common Stock
Equity, Class of Treasury Stock [Line Items]
Common stock share purchase, reduction			100,000
Share Repurchase Plan | Additional Paid-in Capital
Equity, Class of Treasury Stock [Line Items]
Common stock share purchase, reduction			2,200,000
Share Repurchase Plan | Retained Earnings
Equity, Class of Treasury Stock [Line Items]
Common stock share purchase, reduction			$ 12,300,000