Annual report pursuant to Section 13 and 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
Jan. 31, 2018
Jan. 31, 2017
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost $ 52,146 $ 38,540
Gross Unrealized Gains 9 14
Gross Unrealized Losses (63) (8)
Estimated Fair Value 52,092 38,546
Cash [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 39,084 25,576
Estimated Fair Value 39,084 25,576
Cash Equivalents [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 4,568 2,726
Estimated Fair Value 4,568 2,726
Cash and Cash Equivalents [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 43,652 28,302
Estimated Fair Value 43,652 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 (16) (6)
Estimated Fair Value 1,724 1,997
U.S. Government Agency Issues Short Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 1,991 991
Gross Unrealized Gains 9 9
Gross Unrealized Losses (2)  
Estimated Fair Value 1,998 1,000
U.S. Government Agency Issues Long Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 1,002 2,996
Gross Unrealized Losses (17) (2)
Estimated Fair Value 985 $ 2,994
Corporate Bonds Long Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 1,760  
Gross Unrealized Losses (20)  
Estimated Fair Value $ 1,740