Loss Per Share - Additional Information (Detail) - $ / shares			1 Months Ended
	Nov. 01, 2017	May 11, 2016	May 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Earnings Loss Per Share [Line Items]
Common stock par value per share				$ 0.0001	$ 0.0001
IPO [Member]
Earnings Loss Per Share [Line Items]
Number of common stock issued upon conversion of shares		6,900,000	6,900,000
Conversion of convertible preferred stock into common stock		23,481,956	23,481,956
Private Placement [Member]
Earnings Loss Per Share [Line Items]
Number of common stock issued upon conversion of shares		3,055,554	3,055,554
Public Offering [Member] | Underwriting Agreement [Member]
Earnings Loss Per Share [Line Items]
Number of common stock issued upon conversion of shares	6,250,000
Common stock par value per share	$ 0.0001