Balance Sheet Components - Property and Equipment, net (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Property and Equipment, net
Total property and equipment	$ 1,850,000		$ 1,850,000		$ 1,829,000
Less: Accumulated depreciation	(1,071,000)		(1,071,000)		(823,000)
Property and equipment, net	779,000		779,000		1,006,000
Depreciation expense	83,000	$ 86,000	248,000	$ 249,000
Lab equipment
Property and Equipment, net
Total property and equipment	1,825,000		1,825,000		1,804,000
Computer equipment and software
Property and Equipment, net
Total property and equipment	$ 25,000		$ 25,000		$ 25,000