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Summary of Significant Accounting Policies - Additional Information (Detail)
 3 Months Ended 6 Months Ended
Jul. 31, 2013
Jul. 31, 2012
Jul. 31, 2013
Jul. 31, 2012
Summary Of Significant Accounting Policies [Line Items]        
Management agreement, initial term     20 years  
Number of major customers 2 3 2 3
Customer A | Two Major Customers
        
Summary Of Significant Accounting Policies [Line Items]        
Percentage Of Accounts Receivable From Customers 16.90%   16.90%  
Revenue Of Major Customers Percentage Of Total Revenue   15.80%   16.80%
Customer A | Three Major Customers
        
Summary Of Significant Accounting Policies [Line Items]        
Revenue Of Major Customers Percentage Of Total Revenue   25.80%   26.00%
Customer B | Two Major Customers
        
Summary Of Significant Accounting Policies [Line Items]        
Percentage Of Accounts Receivable From Customers 9.50%   9.50%  
Revenue Of Major Customers Percentage Of Total Revenue   15.70%   16.10%
Customer B | Three Major Customers
        
Summary Of Significant Accounting Policies [Line Items]        
Revenue Of Major Customers Percentage Of Total Revenue   11.00%   10.70%
Customer C | Three Major Customers
        
Summary Of Significant Accounting Policies [Line Items]        
Revenue Of Major Customers Percentage Of Total Revenue   10.70%   9.70%