Common Stock and Stockholders' Equity (Deficit) - Stock-based Compensation Expense (Details) - USD ($)
$ in Thousands
3 Months Ended
Apr. 30, 2019
Apr. 30, 2018
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Stock-based compensation expense $ 4,812 $ 3,157
Cost of revenue    
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Stock-based compensation expense 143 61
Research and development    
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Stock-based compensation expense 860 715
Sales and marketing    
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Stock-based compensation expense 1,464 852
General and administrative    
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Stock-based compensation expense $ 2,345 $ 1,529