Subsequent Events - Additional Information (Details) $ / shares in Units, $ in Millions			1 Months Ended
	Oct. 22, 2018 USD ($) $ / shares shares	Oct. 17, 2018 shares	Oct. 31, 2018	Dec. 31, 2027 shares	Nov. 29, 2018 shares	Sep. 30, 2018 shares	Dec. 31, 2017 shares
Subsequent Event [Line Items]
Common stock, shares authorized						20,789,273	20,789,273
2018 Plan | Scenario, Forecast
Subsequent Event [Line Items]
Number of shares of common stock that may be issued				9,694,878
2018 Employee Stock Purchase Plan | Scenario, Forecast
Subsequent Event [Line Items]
Number of shares of common stock that may be issued				490,000
Subsequent Event
Subsequent Event [Line Items]
Common stock, shares authorized					200,000,000
Preferred stock authorized					10,000,000
Subsequent Event | Redeemable Convertible Preferred Stock
Subsequent Event [Line Items]
Number of warrants issued	632,887
Subsequent Event | Weighted-average
Subsequent Event [Line Items]
Exercise price of warrant | $ / shares	$ 0.12
Subsequent Event | 2018 Plan
Subsequent Event [Line Items]
Number of share grants made under the plan		0
Number of shares of common stock that may be issued		3,231,626
Plan description		The number of shares of common stock reserved for issuance under the 2018 Plan will automatically increase on January 1 of each calendar year, starting on January 1, 2019 through January 1, 2028, in an amount equal to 3% of the total number of shares of the Company’s capital stock outstanding on the last day of the calendar month before the date of each automatic increase, or a lesser number of shares determined by the Company’s board of directors.
Share-based payment award, percentage of outstanding stock Maximum		3.00%
Subsequent Event | Initial Public Offering
Subsequent Event [Line Items]
Common stock issued during initial public offering	9,864,666
Sale of stock price per share | $ / shares	$ 5.00
Proceeds from issuance of initial public offering | $	$ 43.0
Warrants converted into shares	13,225,114
Subsequent Event | 2018 Employee Stock Purchase Plan
Subsequent Event [Line Items]
Number of shares of common stock that may be issued		196,000
Plan description		The number of shares of common stock reserved for issuance will automatically increase on January 1 of each calendar year, beginning on January 1, 2019 through January 1, 2028, by the lesser of (1) 1% of the total number of shares of the Company’s common stock outstanding on the last day of the calendar month before the date of the automatic increase, and (2) 490,000 shares; provided that before the date of any such increase, the Company’s board of directors may determine that such increase will be less than the amount set forth in clauses (1) and (2).
Share-based payment award, percentage of outstanding stock Maximum		1.00%
Common stock purchased		0
Subsequent Event | Common Stock
Subsequent Event [Line Items]
Reverse stock split conversion ratio			11.0634
Warrants converted into shares	632,887
Subsequent Event | Common Stock | Initial Public Offering
Subsequent Event [Line Items]
Warrants converted into shares	632,888