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
Apr. 30, 2018
Jan. 31, 2018
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost $ 49,178 $ 52,146
Gross Unrealized Gains 9 9
Gross Unrealized Losses (92) (63)
Estimated Fair Value 49,095 52,092
Cash [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 36,071 39,084
Estimated Fair Value 36,071 39,084
Cash Equivalents [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 2,776 4,568
Gross Unrealized Gains 9  
Estimated Fair Value 2,785 4,568
Cash and Cash Equivalents [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 38,847 43,652
Gross Unrealized Gains 9  
Estimated Fair Value 38,856 43,652
U.S. Treasury Notes and Bonds - Short Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 2,250 2,001
Gross Unrealized Losses (13) (8)
Estimated Fair Value 2,237 1,993
U.S. Treasury Notes and Bonds - Long Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 4,264 1,740
Gross Unrealized Losses (28) (16)
Estimated Fair Value 4,236 1,724
U.S. Government Agency Issues Short Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 500 1,991
Gross Unrealized Gains   9
Gross Unrealized Losses (1) (2)
Estimated Fair Value 499 1,998
U.S. Government Agency Issues Long Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 1,002 1,002
Gross Unrealized Losses (19) (17)
Estimated Fair Value 983 985
Corporate Bonds Long Term [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 2,315 1,760
Gross Unrealized Losses (31) (20)
Estimated Fair Value $ 2,284 $ 1,740