Balance Sheet Components - Property and Equipment (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Land, Property and Equipment
Total property and equipment at cost	$ 942,000		$ 935,000
Accumulated depreciation	(235,000)		(225,000)
Property and equipment, net	707,000		710,000
Depreciation and amortization expense	10,000	$ 15,000
Land
Land, Property and Equipment
Total property and equipment at cost	396,000		396,000
Lab equipment
Land, Property and Equipment
Total property and equipment at cost	418,000		411,000
Clinical equipment
Land, Property and Equipment
Total property and equipment at cost	65,000		65,000
Software
Land, Property and Equipment
Total property and equipment at cost	$ 63,000		$ 63,000