Consolidated Balance Sheets and Statements of Operations and Comprehensive Loss Components - Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accrued expenses and other:
Accrued wages and employee benefits	$ 616	$ 1,051
Accrued restructuring liabilities	478	5
Interest payable	346	314
IC development and wafer purchase costs	335	598
Professional fees, legal and consulting	182	282
Corporate taxes	153	52
Employee stock purchase plan withholdings		200
Other	397
Total	$ 2,507	$ 2,502