Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Compensation - Summary of Stock-based Compensation Expense (Detail)

v3.8.0.1
Stock-Based Compensation - Summary of Stock-based Compensation Expense (Detail) - Omnibus Plan [Member]
$ in Thousands
3 Months Ended
Mar. 31, 2018
USD ($)
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]  
Stock-based compensation expense $ 68
Selling, General and Administrative [Member]  
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]  
Stock-based compensation expense 369
Research and Development [Member]  
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]  
Stock-based compensation expense 437
Employee Stock Options [Member]  
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]  
Stock-based compensation expense 298
Employee Restricted Stock Units [Member]  
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]  
Stock-based compensation expense 435
Nonemployee Stock Options [Member]  
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]  
Stock-based compensation expense 712
Nonemployee Restricted Stock Units [Member]  
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]  
Stock-based compensation expense $ 89