Selected Balance Sheet Components - Schedule of property and equipment, net (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Property and equipment, net:
Financing right-of-use lease	$ 138		$ 148
Total property and equipment, gross	17,052		16,364
Less accumulated depreciation	(9,629)		(9,220)
Property and equipment, net	7,423		7,144
Depreciation expense	500	$ 300
Machinery and equipment
Property and equipment, net:
Total property and equipment, gross	3,096		3,152
Furniture, fixtures and office equipment
Property and equipment, net:
Total property and equipment, gross	810		775
Computer equipment and software
Property and equipment, net:
Total property and equipment, gross	6,220		6,174
Leasehold improvements
Property and equipment, net:
Total property and equipment, gross	5,256		5,256
Construction in process
Property and equipment, net:
Total property and equipment, gross	$ 1,532		$ 859