Balance Sheet Components - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Accrued liabilities
Accrued payroll-related expenses	$ 1,088	$ 1,088	$ 1,236
Accrued joint development agreement expenses			170
Accrued inventory	311	311	87
Restructuring expenses			782
Other	309	309	452
Total accrued liabilities	1,708	1,708	$ 2,727
Payment of employee severance and benefit arrangements	$ 60	$ 800