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Marketable Securities and Fair Value Measurements - Summary of Marketable Securities (Details) - USD ($)
$ in Thousands
Jan. 31, 2016
Jan. 31, 2015
Jan. 31, 2014
Schedule Of Available For Sale Securities [Line Items]      
Amortized Cost $ 7,381    
Unrealized Loss (2)    
Marketable securities 7,379 $ 0 $ 0
Corporate Debt Securities      
Schedule Of Available For Sale Securities [Line Items]      
Amortized Cost 5,560    
Unrealized Loss (1)    
Marketable securities 5,559    
Asset-backed Securities      
Schedule Of Available For Sale Securities [Line Items]      
Amortized Cost 1,821    
Unrealized Loss (1)    
Marketable securities $ 1,820