Fair Value Measurements - Schedule of Reconciliation of Preferred Stock Warrant Liability Measured at Fair Value Using Significant Unobservable Inputs (Details) - Preferred Stock Warrant Liability - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Beginning balance	$ 414	$ 357
Changes in fair value of underlying warrant securities, recorded to interest expense	202	57
Conversion of warrant, recorded to additional paid-in capital	(616)
Ending balance	$ 0	$ 414