Quarterly report pursuant to Section 13 or 15(d)

Stock Based Compensation - Summary of Fair Values of Stock Options Granted (Detail)

v3.8.0.1
Stock Based Compensation - Summary of Fair Values of Stock Options Granted (Detail) - Employee Stock Option [Member] - $ / shares
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Stock price $ 22.34 $ 17.59
Dividend yield 0.00% 0.00%
Expected volatility 177.00% 66.00%
Risk-free interest rate 1.61% 0.62%
Expected life 6 months 6 months