Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Stock Option Activity (Detail)

v3.19.1
Stockholders' Equity - Stock Option Activity (Detail) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2019
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Number of shares, Options vested and expected to vest 1,085,501  
Number of shares, Options exercised 0  
Number of shares, Options vested and expected to vest 1,085,501 1,085,501
Number of shares, Options Exercisable 1,085,501  
Weighted average exercise price, Options vested and expected to vest $ 3.75  
Weighted Average Exercise Price, Options exercised 0  
Weighted average exercise price, Options vested and expected to vest 3.75  
Weighted average exercise price, Options vested and exercisable $ 3.75  
Total Weighted average intrinsic value, Options vested and expected to vest $ 155,322 $ 0
Total Weighted Average Intrinsic Value, Options exercised 0  
Total weighted average intrinsic value, Exercisable $ 155,322  
Weighted average remaining contractual life (years), Options vested and expected to vest 2 years 8 months 4 days 2 years 11 months 4 days
Weighted average remaining contractual life (years), Options vested and exercisable 2 years 8 months 4 days