Summary of Significant Accounting Policies - Schedule of Change in Fair Value of Liability (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Redeemable convertible preferred stock warrant
Reclassification to additional paid-in capital	$ 65
Redeemable Convertible Preferred Stock Warrants | Level 3
Redeemable convertible preferred stock warrant
Beginning balance	437	$ 145	$ 45
Issuance of redeemable convertible preferred stock warrants / derivative liability		307	106
Change in fair value recorded in other income (expense), net	372	15	6
Reclassification to additional paid-in capital	(65)
Ending balance		$ 437	$ 145
Derivative Liability | Level 3
Redeemable convertible preferred stock warrant
Issuance of redeemable convertible preferred stock warrants / derivative liability	918
Change in fair value recorded in other income (expense), net	(798)
Reclassification to additional paid-in capital	$ (120)