Balance Sheets Components - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Prepaid Expense And Other Assets Current [Abstract]
Advance to suppliers	$ 587	$ 853
Prepaid expenses	1,105	1,074
Other current assets	885	722
Total prepaid expenses and other current assets	$ 2,577	$ 2,649