v3.21.1
Background and liquidity (Detail) - USD ($)
$ / shares in Units, $ in Thousands
 1 Months Ended 12 Months Ended
Oct. 23, 2020
Dec. 17, 2019
Jul. 22, 2019
Oct. 31, 2020
Jan. 31, 2021
Jan. 31, 2020
Jan. 31, 2019
Subsidiary, Sale of Stock [Line Items]              
Issuance of common stock, net of issuance costs (in shares) 5,750,000     5,750,000      
Issue price per share (in USD per share) $ 32.00     $ 32.00      
Payment of offering costs         $ 290 $ 6,217 $ 195
Dividend paid         0 14,955 0
Net proceeds after discounts and offering expenses $ 174,510     $ 174,800 $ 174,800 $ 130,781 $ 0
Number of months with sufficient funds to operate         12 months    
Common stock              
Subsidiary, Sale of Stock [Line Items]              
Issuance of common stock, net of issuance costs (in shares)   7,762,500     5,750,000 7,812,500  
Payment of offering costs   $ 1,047          
Conversion of preferred stock into common stock and cancellation of redeemable preferred stock (in shares)           25,311,535  
IPO              
Subsidiary, Sale of Stock [Line Items]              
Conversion of preferred stock into common stock and cancellation of redeemable preferred stock (in shares)     588,763        
Dividend paid     $ 14,955        
IPO | Common stock              
Subsidiary, Sale of Stock [Line Items]              
Issuance of common stock, net of issuance costs (in shares)     7,812,500        
Issue price per share (in USD per share)     $ 18.00        
Proceeds from issuance of common stock in equity offerings, net of underwriters' discounts and commissions     $ 130,781        
Underwriting discounts and commission     9,844        
Payment of offering costs     $ 6,412        
IPO | Common stock | Certain Selling Stockholders              
Subsidiary, Sale of Stock [Line Items]              
Issuance of common stock, net of issuance costs (in shares)     2,868,923