Balance Sheet Components - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Accrued liabilities
Accrued payroll-related expenses	$ 755	$ 755	$ 1,236
Accrued joint development agreement expenses			170
Accrued inventory	252	252	87
Restructuring expenses	67	67	782
Other	318	318	452
Total accrued liabilities	1,392	1,392	$ 2,727
Payment of employee severance and benefit arrangements	$ 300	$ 700