v3.20.1
Fair Value Measurements and Marketable Securities - Unobservable Input Reconciliation (Details) - USD ($)
$ in Thousands
 12 Months Ended
Jan. 31, 2020
Jan. 31, 2019
Jan. 31, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Adjustment resulting from change in fair value recognized in the consolidated statement of operations $ 6,000 $ 3,600 $ 300
Reclassification of redeemable convertible preferred stock warrant liability to additional paid-in capital upon IPO (10,559) 0 0
Shares of common stock issuable upon conversion of redeemable convertible preferred stock warrants | Fair Value, Inputs, Level 3      
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair value, measurement with unobservable inputs reconciliation, recurring basis, beginning balance 4,537 961 568
Additions 0 0 129
Adjustment resulting from change in fair value recognized in the consolidated statement of operations 6,022 3,576 264
Fair value, measurement with unobservable inputs reconciliation, recurring basis,, ending balance $ 0 $ 4,537 $ 961