Balance Sheet Components - Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Accrued sales commission payable	$ 389	$ 387
Accrued manufacturing expenses	1,106	692
Deferred rent, current portion		514
Liabilities to certain customers	4,144	366
Warranty reserve	513	505
Deferred revenue, current portion	415	1,848
Income tax payable	132	172
Interest payable	950
Other accrued liabilities	1,719	688
Total accrued expenses and other current liabilities	$ 9,368	$ 5,172