Annual report pursuant to Section 13 and 15(d)

Employee Benefit Plan - Additional Information (Detail)

v3.8.0.1
Employee Benefit Plan - Additional Information (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Defined Contribution Plan Disclosure [Line Items]      
Defined contribution plan description The Company provides a 401(k) defined contribution plan (the Plan) for participation by all regular fulltime employees who have completed three months of service    
Percentage of matching contribution to plan 100.00%    
Percentage of salary for matching contribution per employee 3.00%    
Percentage of additional matching contribution to plan 50.00%    
Contributions to the plan by employer $ 93 $ 66 $ 47
Minimum [Member]      
Defined Contribution Plan Disclosure [Line Items]      
Percentage of salary for additional matching contribution per employee 3.00%    
Maximum [Member]      
Defined Contribution Plan Disclosure [Line Items]      
Percentage of salary for additional matching contribution per employee 5.00%