Employee Benefit Plan - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Eligible age for employees for participating in the plan	21 years
Company's contributions to employee benefit plan	$ 0	$ 3,700
Future
Defined Benefit Plan Disclosure [Line Items]
Company's contributions to employee benefit plan	$ 3,500