Quarterly report pursuant to Section 13 or 15(d)

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

v3.10.0.1
Fair Value Measurements - Summary of Available-for-Sale Securities (Detail) - USD ($)
$ in Thousands
Oct. 31, 2018
Jan. 31, 2018
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost $ 31,909 $ 52,146
Gross Unrealized Gains 11 9
Gross Unrealized Losses (80) (63)
Estimated Fair Value 31,840 52,092
Cash [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 18,723 39,084
Estimated Fair Value 18,723 39,084
Cash Equivalents [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 2,820 4,568
Gross Unrealized Gains 11  
Estimated Fair Value 2,831 4,568
Cash and Cash Equivalents [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 21,543 43,652
Gross Unrealized Gains 11  
Estimated Fair Value 21,554 43,652
U.S. Treasury Notes and Bonds - Short Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 749 2,001
Gross Unrealized Losses (3) (8)
Estimated Fair Value 746 1,993
U.S. Treasury Notes and Bonds - Long Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 6,306 1,740
Gross Unrealized Losses (32) (16)
Estimated Fair Value 6,274 1,724
U.S. Government Agency Issues Short Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 1,001 1,991
Gross Unrealized Gains   9
Gross Unrealized Losses (15) (2)
Estimated Fair Value 986 1,998
U.S. Government Agency Issues Long Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost   1,002
Gross Unrealized Losses   (17)
Estimated Fair Value   985
Corporate Bonds Long Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 2,310 1,760
Gross Unrealized Losses (30) (20)
Estimated Fair Value $ 2,280 $ 1,740