Condensed Balance Sheet Components - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Accrued Liabilities And Other Liabilities [Abstract]
Accrued research and development costs	$ 5,498	$ 3,968
Accrued other current liabilities	5,365	433
Accrued employee related expenses	1,210	1,865
Liability for unvested stock, short-term	133	143
Total accrued expenses and other current liabilities	$ 12,206	$ 6,409