Benefit Plan - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation	$ 47,000	$ 48,000
General Discussion of Pension and Other Postretirement Benefits	We make matching contributions equal to 100% of the first 3% and 50% of the next 2% of each employee’s base salary up to the allowable amount which is fully vested on the date the matching contributions are made.