Net Loss per Share - Additional Information (Detail) - shares				1 Months Ended	6 Months Ended
	Jul. 23, 2018	Jul. 18, 2018	Apr. 05, 2017	Jul. 31, 2018	Jun. 30, 2018	Jun. 30, 2017
Employee Options [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Anti-dilutive common stock equivalents					3,871,194	3,118,786
Common Stock [Member] | Subsequent Event [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Common stock, shares issued		5,175,000
Common Stock [Member] | Follow-on Public Offering [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Common stock, shares issued			5,117,500			5,117,500
Common Stock [Member] | Follow-on Public Offering [Member] | Subsequent Event [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Common stock, shares issued	5,175,000			5,175,000
Common Stock [Member] | Underwriter's Over-Allotment [Member] | Subsequent Event [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Common stock, shares issued	675,000	675,000		675,000