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Stockholders' Equity - Valuation Assumptions (Details) - ESPP - $ / shares
12 Months Ended
Jan. 31, 2021
Jan. 31, 2020
Jan. 31, 2019
Class of Stock [Line Items]      
Risk-free interest rate, minimum 0.11% 1.92%  
Risk-free interest rate, maximum 0.17% 2.52%  
Risk-free interest rate     2.33%
Expected dividend yield 0.00% 0.00% 0.00%
Expected life of purchase right (in years) 6 months 6 months 6 months
Expected volatility, minimum 47.00% 39.00%  
Expected volatility, maximum 58.00% 52.00%  
Expected volatility     40.00%
Granted (in usd per share)     $ 14.24
Minimum      
Class of Stock [Line Items]      
Granted (in usd per share) $ 90.15 $ 14.88  
Maximum      
Class of Stock [Line Items]      
Granted (in usd per share) $ 221.20 $ 18.56