Balance Sheet Accounts - Accrued Liabilities (Details) - USD ($) $ in Thousands |
Mar. 31, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Accrued Liabilities [Abstract] | ||
| Performance bonus | $ 1,181 | $ 2,080 |
| Payroll and related expenses | 2,892 | 1,996 |
| Bonus feature of stock option grants | 4,490 | 4,212 |
| Commissions | 379 | 522 |
| Professional and legal services | 367 | 500 |
| Short-term minimum lease payments under capital leases | 184 | 258 |
| Warranty reserve | 326 | 313 |
| Advisory board and board of director related expenses | 145 | 124 |
| Other | 591 | 672 |
| Accrued liabilities | $ 10,555 | $ 10,677 |