Selected Balance Sheet Components - Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property and equipment, net:
Total property and equipment, gross	$ 10,968	$ 9,687
Accumulated depreciation	(7,093)	(5,638)
Property and Equipment	3,875	4,049
Depreciation expense	1,600	1,300	$ 800
Machinery and equipment
Property and equipment, net:
Total property and equipment, gross	3,150	3,280
Furniture, fixtures and office equipment
Property and equipment, net:
Total property and equipment, gross	931	931
Computer equipment and software
Property and equipment, net:
Total property and equipment, gross	3,147	2,662
Leasehold improvements
Property and equipment, net:
Total property and equipment, gross	3,332	2,393
Construction in process
Property and equipment, net:
Total property and equipment, gross	$ 408	$ 421