Balance Sheet Components - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Accrued liabilities
Accrued payroll-related expenses	$ 819	$ 1,236
Accrued joint development agreement expenses		170
Accrued inventory	267	87
Restructuring expenses	409	782
Other	470	452
Total accrued liabilities	1,965	$ 2,727
Payment of employee severance and benefit arrangements	$ 373