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CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS (Details) - USD ($)
12 Months Ended
Jan. 31, 2016
Jan. 31, 2015
Jan. 31, 2014
Jan. 31, 2013
Cash and Cash Equivalents        
Minimum percentage of cash and cash equivalents secured by U.S. Government obligations 80.00% 80.00%    
Weighted average annual interest rate on CDs (as a percent) 0.63%      
Cash, cash equivalents $ 160,909,000 $ 333,691,000 $ 272,209,000 $ 175,142,000
Joint Venture        
Cash and Cash Equivalents        
Cash, cash equivalents 41,757,000      
Short-term investments 9,006,000      
Held-to-maturity Securities        
Cash and Cash Equivalents        
Accrued interest on held-to-maturity securities $ 98,000      
Held-to-maturity Securities | Minimum        
Cash and Cash Equivalents        
Maturity period 3 months      
Held-to-maturity Securities | Maximum        
Cash and Cash Equivalents        
Maturity period 12 months