Fair Value Measurements - Schedule of Reconciliation of Changes in the Fair Value of Financial Instruments (Details)	9 Months Ended
	Sep. 30, 2017 USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Change in fair value associated with convertible preferred stock tranche liability	$ 876,000
Reduction in tranche liability due to preferred stock issuance	(5,123,000)
Significant Unobservable Inputs (Level 3)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value as of January 1, 2017	4,247,000
Change in fair value associated with convertible preferred stock tranche liability	876,000
Reduction in tranche liability due to preferred stock issuance	$ (5,123,000)