Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Fair Value of Financial Assets and Liabilities Measured on Recurring Basis (Detail)

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Fair Value Measurements - Fair Value of Financial Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($)
$ in Thousands
Apr. 30, 2017
Jan. 31, 2017
Available-for-sale marketable securities:    
Marketable securities, short-term $ 7,245 $ 5,253
Non-current marketable securities:    
Marketable securities, long-term 2,989 4,991
Total 12,974 12,970
U.S. Treasury Notes and Bonds Conventional [Member]    
Available-for-sale marketable securities:    
Marketable securities, short-term 4,748 4,253
Non-current marketable securities:    
Marketable securities, long-term 1,495 1,997
U.S. Government Agency Issues Short Term [Member]    
Available-for-sale marketable securities:    
Marketable securities, short-term 2,497 1,000
U.S. Government Agency Issues Long Term [Member]    
Non-current marketable securities:    
Marketable securities, long-term 1,494 2,994
Money Market Accounts [Member]    
Financial assets:    
Cash and cash equivalents 2,740 2,726
Fair Value, Inputs, Level 1 [Member]    
Non-current marketable securities:    
Total 8,983 8,976
Fair Value, Inputs, Level 1 [Member] | U.S. Treasury Notes and Bonds Conventional [Member]    
Available-for-sale marketable securities:    
Marketable securities, short-term 4,748 4,253
Non-current marketable securities:    
Marketable securities, long-term 1,495 1,997
Fair Value, Inputs, Level 1 [Member] | Money Market Accounts [Member]    
Financial assets:    
Cash and cash equivalents 2,740 2,726
Fair Value, Inputs, Level 2 [Member]    
Non-current marketable securities:    
Total 3,991 3,994
Fair Value, Inputs, Level 2 [Member] | U.S. Government Agency Issues Short Term [Member]    
Available-for-sale marketable securities:    
Marketable securities, short-term 2,497 1,000
Fair Value, Inputs, Level 2 [Member] | U.S. Government Agency Issues Long Term [Member]    
Non-current marketable securities:    
Marketable securities, long-term $ 1,494 $ 2,994