Fair Value Measurements - Assets measured on a recurring basis on year end - (Details) $ in Thousands	Dec. 31, 2015 USD ($)
Liabilities, Fair Value Disclosure [Abstract]
Convertible preferred stock tranche liability	$ 6,305
Total liabilities measured at fair value	6,305
Level 3
Liabilities, Fair Value Disclosure [Abstract]
Convertible preferred stock tranche liability	6,305
Total liabilities measured at fair value	$ 6,305