Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Fair Value of Financial Assets Measured on Recurring Basis (Detail)

v3.19.1
Fair Value Measurements - Fair Value of Financial Assets Measured on Recurring Basis (Detail) - USD ($)
$ in Thousands
Apr. 30, 2019
Jan. 31, 2019
Marketable securities:    
Marketable securities $ 9,644 $ 10,359
U.S. Treasury Notes and Bonds [Member]    
Marketable securities:    
Marketable securities 6,350 7,072
U.S. Agency Bonds [Member]    
Marketable securities:    
Marketable securities 995 992
Corporate Bonds [Member]    
Marketable securities:    
Marketable securities 2,299 2,295
Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash equivalents 3,690 2,887
Marketable securities:    
Total 13,334 13,246
Fair Value, Measurements, Recurring [Member] | U.S. Treasury Notes and Bonds [Member]    
Marketable securities:    
Marketable securities 6,350 7,072
Fair Value, Measurements, Recurring [Member] | U.S. Agency Bonds [Member]    
Marketable securities:    
Marketable securities 995 992
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member]    
Marketable securities:    
Marketable securities 2,299 2,295
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]    
Assets:    
Cash equivalents 2,723 2,724
Marketable securities:    
Total 9,073 9,796
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. Treasury Notes and Bonds [Member]    
Marketable securities:    
Marketable securities 6,350 7,072
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]    
Assets:    
Cash equivalents 967 163
Marketable securities:    
Total 4,261 3,450
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. Agency Bonds [Member]    
Marketable securities:    
Marketable securities 995 992
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Bonds [Member]    
Marketable securities:    
Marketable securities $ 2,299 $ 2,295