Balance Sheet Components - Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Prepaid services	$ 316	$ 88
Deferred offering costs	65	114
Prepaid software and subscriptions	61	42
Prepaid insurance	49	45
Other	6	69
Total	$ 497	$ 358