Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Stock Option Activity (Detail)

v3.8.0.1
Stockholders' Equity - Stock Option Activity (Detail) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 12 Months Ended
Mar. 31, 2018
Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Number of shares, Options Outstanding 1,110,501  
Number of shares, Options Exercised 0  
Number of shares, Options Outstanding 1,110,501 1,110,501
Number of shares, Options Exercisable 1,085,501  
Weighted Average Exercise Price, Options Exercised $ 0  
Total Weighted Average Intrinsic Value, Options Exercised $ 0  
Total Weighted Average Intrinsic Value, Options vested and exercisable $ 1,701,361  
Weighted Average Remaining Contractual Life, Options Exercisable 3 years 8 months 16 days 3 years 11 months 12 days
Weighted average exercise price, Options vested and expected to vest $ 3.78  
Weighted average exercise price, Options vested and expected to vest 3.78 $ 3.78
Weighted average exercise price, Options vested and exercisable $ 3.75  
Total Weighted average intrinsic value, Options vested and expected to vest $ 1,351,080  
Total Weighted average intrinsic value, Options vested and expected to vest $ 1,701,361 $ 1,351,080
Weighted average remaining contractual life (years), Options vested and expected to vest 3 years 8 months 16 days 3 years 11 months 12 days
Weighted average remaining contractual life (years), Options vested and exercisable 3 years 8 months 5 days