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
Jul. 31, 2017
Jan. 31, 2017
Available-for-sale marketable securities:    
Marketable securities, short-term $ 4,543 $ 5,253
Non-current marketable securities:    
Marketable securities, long-term 5,744 4,991
Total 12,988 12,970
U.S. Treasury Notes and Bonds Conventional [Member]    
Available-for-sale marketable securities:    
Marketable securities, short-term 1,547 4,253
Non-current marketable securities:    
Marketable securities, long-term 2,986 1,997
U.S. Government Agency Issues Short Term [Member]    
Available-for-sale marketable securities:    
Marketable securities, short-term 2,996 1,000
U.S. Government Agency Issues Long Term [Member]    
Non-current marketable securities:    
Marketable securities, long-term 996 2,994
Corporate Bonds [Member]    
Non-current marketable securities:    
Marketable securities, long-term 1,762  
Cash Equivalents [Member]    
Financial assets:    
Cash equivalents 2,701 2,726
Fair Value, Inputs, Level 1 [Member]    
Non-current marketable securities:    
Total 6,531 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 1,547 4,253
Non-current marketable securities:    
Marketable securities, long-term 2,986 1,997
Fair Value, Inputs, Level 1 [Member] | Cash Equivalents [Member]    
Financial assets:    
Cash equivalents 1,998 2,726
Fair Value, Inputs, Level 2 [Member]    
Non-current marketable securities:    
Total 6,457 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 2,996 1,000
Fair Value, Inputs, Level 2 [Member] | U.S. Government Agency Issues Long Term [Member]    
Non-current marketable securities:    
Marketable securities, long-term 996 $ 2,994
Fair Value, Inputs, Level 2 [Member] | Corporate Bonds [Member]    
Non-current marketable securities:    
Marketable securities, long-term 1,762  
Fair Value, Inputs, Level 2 [Member] | Cash Equivalents [Member]    
Financial assets:    
Cash equivalents $ 703