Selected Balance Sheet Components - Schedule of property and equipment, net (Details) - USD ($) $ in Thousands	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:
Financing right-of-use lease	$ 120		$ 120		$ 148
Total property and equipment, gross	17,824		17,824		16,364
Less accumulated depreciation	(10,709)		(10,709)		(9,220)
Property and equipment, net	7,115		7,115		7,144
Depreciation expense	600	$ 400	1,600	$ 1,200
Machinery and equipment
Property and equipment, net:
Total property and equipment, gross	3,683		3,683		3,152
Furniture, fixtures and office equipment
Property and equipment, net:
Total property and equipment, gross	810		810		775
Computer equipment and software
Property and equipment, net:
Total property and equipment, gross	6,585		6,585		6,174
Leasehold improvements
Property and equipment, net:
Total property and equipment, gross	5,436		5,436		5,256
Construction in process
Property and equipment, net:
Total property and equipment, gross	$ 1,190		$ 1,190		$ 859