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Short-Term Borrowings - Additional Information (Detail) (Revolving credit facility, USD $)
In Thousands, unless otherwise specified
2 Months Ended 6 Months Ended
Jul. 31, 2013
Jul. 31, 2013
Line of Credit Facility [Line Items]    
Termination date for senior, unsecured revolving credit facility May 24, 2017  
Revolving credit facility, maximum borrowing capacity $ 125,000 $ 125,000
Credit facility limits, aggregate amount available for dividend and repurchase of stock   $ 50,000
Credit facility limits, aggregate amount available for dividend and repurchase of stock, percentage of cumulative net income   70.00%
Minimum
   
Line of Credit Facility [Line Items]    
Commitment fee percentage on unused line of credit 0.30%  
Minimum | L I B O R
   
Line of Credit Facility [Line Items]    
Debt instrument, basis spread 2.00%  
Minimum | Base rate
   
Line of Credit Facility [Line Items]    
Debt instrument, basis spread 1.00%  
Maximum
   
Line of Credit Facility [Line Items]    
Commitment fee percentage on unused line of credit 0.40%  
Maximum | L I B O R
   
Line of Credit Facility [Line Items]    
Debt instrument, basis spread 2.50%  
Maximum | Base rate
   
Line of Credit Facility [Line Items]    
Debt instrument, basis spread 1.50%