Fair Value Measurements - Summary of Change in Derivative Liability (Details) - Derivative Liability $ in Thousands |
12 Months Ended |
---|---|
Dec. 31, 2018
USD ($)
| |
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | |
Fair Value at beginning of period | $ 1,886 |
Bifurcated derivative liability | 113 |
Change in fair value | 206 |
Conversion of promissory notes to Series B redeemable convertible preferred stock | $ (2,205) |