Organization and Description of Business - Additional Information (Details) $ in Thousands	1 Months Ended		9 Months Ended
	Oct. 31, 2019 USD ($)	Oct. 31, 2018	Sep. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Organization and Description of Business [Line Item]
Reverse stock split description			The Company effected a 11.0634-for-1 reverse split of its outstanding common stock and redeemable convertible preferred stock.
Accumulated deficit			$ (150,827)	$ (122,911)
Cash and cash equivalents			81,771	$ 61,051	$ 24,341	$ 13,406
Working capital			$ 77,400
Subsequent Event
Organization and Description of Business [Line Item]
Proceeds from borrowings under term loan	$ 5,000
Common Stock
Organization and Description of Business [Line Item]
Reverse stock split conversion ratio		11.0634