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Shareholder's Equity - Additional Information (Detail) (USD $)
In Thousands, except Share data, unless otherwise specified
3 Months Ended 3 Months Ended
Apr. 30, 2014
Jan. 31, 2014
Aug. 27, 2013
Apr. 30, 2013
May 27, 2014
Subsequent Event
Apr. 30, 2014
Employee Stock
Equity, Class of Treasury Stock [Line Items]            
Common shares authorized for repurchase, shares     10,000,000   10,000,000  
Stock repurchased and retired during period, common shares 9,699,700         1,690
Stock repurchased and retired during period, total cost $ 353,315         $ 61
Average cost per share $ 36.43          
Additional paid-in-capital 0 97,684   74,618    
Retained earnings reduction related to shares repurchased $ 250,246