Quarterly report pursuant to Section 13 or 15(d)

Fair Value (Details)

v2.4.0.8
Fair Value (Details) (USD $)
In Thousands, unless otherwise specified
Oct. 31, 2013
Jan. 31, 2013
Assets:    
Total assets measured at fair value $ 32,917 $ 66,269
Money market funds
   
Assets:    
Total assets measured at fair value 27,468 32,522
Commercial paper
   
Assets:    
Total assets measured at fair value 4,749 24,092
Corporate debt securities
   
Assets:    
Total assets measured at fair value 700 9,655
Quoted Prices in Active Markets for Identical Instruments (Level 1)
   
Assets:    
Total assets measured at fair value 27,468 32,522
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Money market funds
   
Assets:    
Total assets measured at fair value 27,468 32,522
Significant Other Observable Inputs (Level 2)
   
Assets:    
Total assets measured at fair value 5,449 33,747
Significant Other Observable Inputs (Level 2) | Commercial paper
   
Assets:    
Total assets measured at fair value 4,749 24,092
Significant Other Observable Inputs (Level 2) | Corporate debt securities
   
Assets:    
Total assets measured at fair value 700 9,655
Total
   
Assets:    
Total assets measured at fair value 32,917 66,269
Total | Money market funds
   
Assets:    
Total assets measured at fair value 27,468 32,522
Total | Commercial paper
   
Assets:    
Total assets measured at fair value 4,749 24,092
Total | Corporate debt securities
   
Assets:    
Total assets measured at fair value $ 700 $ 9,655