Fair Value Measurements - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Loss on remeasurement of convertible preferred stock warrant liability		$ 3,725,000	$ 524,000
Reclassification of convertible preferred stock warrant liability into additional paid-in capital	$ 5,700,000	5,711,000
Transfers into or out of level 3		0
Other Expense, Net
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Loss on remeasurement of convertible preferred stock warrant liability		$ 3,700,000