Stockholders' Equity (Deficit) - Common Stock Reserved for Future Issuance (Details) - shares shares in Thousands	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Redeemable convertible preferred stock		8,148
Warrants to purchase convertible preferred stock		372
Common stock warrants	841
Common stock options issued and outstanding	1,958	504
Common stock available for future issuance	3,294	9,104
Equity incentive plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock available for future issuance	495	80