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Share-Based Compensation - Schedule of Fair Value of Stock Option Award Granted Estimated on Date of Grant Using the Black-Scholes-Merton Option Pricing Model (Detail) - $ / shares
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]      
Risk-free interest rate 1.30% 1.60% 1.40%
Weighted average volatility 70.40% 73.20% 73.00%
Expected life (in years) 4 years 9 months 18 days 5 years 1 month 6 days 4 years 3 months 18 days
Weighted average grant date fair value per share of options granted $ 2.75 $ 2.86 $ 3.89