Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Summary of Available-for-Sale Securities (Detail)

v3.8.0.1
Fair Value Measurements - Summary of Available-for-Sale Securities (Detail) - USD ($)
$ in Thousands
Oct. 31, 2017
Jan. 31, 2017
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost $ 36,641 $ 38,540
Gross Unrealized Gains 18 14
Gross Unrealized Losses (29) (8)
Estimated Fair Value 36,630 38,546
Cash [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 23,605 25,576
Estimated Fair Value 23,605 25,576
Cash Equivalents [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 3,549 2,726
Gross Unrealized Gains 1  
Estimated Fair Value 3,550 2,726
Cash and Cash Equivalents [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 27,154 28,302
Gross Unrealized Gains 1  
Estimated Fair Value 27,155 28,302
U.S. Treasury Notes and Bonds - Short Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 2,001 4,248
Gross Unrealized Gains   5
Gross Unrealized Losses (8)  
Estimated Fair Value 1,993 4,253
U.S. Treasury Notes and Bonds - Long Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 1,740 2,003
Gross Unrealized Losses (5) (6)
Estimated Fair Value 1,735 1,997
U.S. Government Agency Issues Short Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 2,982 991
Gross Unrealized Gains 17 9
Gross Unrealized Losses (2)  
Estimated Fair Value 2,997 1,000
U.S. Government Agency Issues Long Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 1,003 2,996
Gross Unrealized Losses (10) (2)
Estimated Fair Value 993 $ 2,994
Corporate Bonds Long Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 1,761  
Gross Unrealized Losses (4)  
Estimated Fair Value $ 1,757