Balance Sheet Components - Property and Equipment, Net (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property and Equipment
Total property and equipment	$ 4,322,000	$ 2,938,000
Less: accumulated depreciation and amortization	(2,641,000)	(2,077,000)
Property and equipment, net	1,681,000	861,000
Property and equipment income statement disclosure
Depreciation expense	703,000	527,000	$ 406,000
Laboratory equipment
Property and Equipment
Total property and equipment	2,947,000	2,533,000
Furniture and computer equipment
Property and Equipment
Total property and equipment	512,000	338,000
Leasehold improvements
Property and Equipment
Total property and equipment	863,000	67,000
Australia
Property and Equipment
Property and equipment, net	$ 37,000	$ 200	$ 1,200