Selected Balance Sheet Components - Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Property and equipment, net:
Total property and equipment, gross	$ 15,863		$ 15,863		$ 13,411
Financing right-of-use lease	157		157		0
Less: Accumulated depreciation	(8,673)		(8,673)		(7,505)
Total, net	7,190		7,190		5,906
Depreciation and amortization	400	$ 300	1,200	$ 1,100
Machinery and equipment
Property and equipment, net:
Total property and equipment, gross	2,577		2,577		1,536
Furniture, fixtures and office equipment
Property and equipment, net:
Total property and equipment, gross	775		775		775
Computer equipment and software
Property and equipment, net:
Total property and equipment, gross	6,007		6,007		3,712
Leasehold improvements
Property and equipment, net:
Total property and equipment, gross	4,631		4,631		4,587
Construction in process
Property and equipment, net:
Total property and equipment, gross	$ 1,716		$ 1,716		$ 2,801