Balance Sheets Details - Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Balance Sheet Related Disclosures [Abstract]
Accrued purchase	$ 67	$ 430
Accrued professional and outside service fees	746	498
Deferred rent	168	143
Lease incentive obligation	425	425
Other	705	517
Total	$ 2,111	$ 2,013