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Stock-Based Compensation - Schedule of Fair Value Option Award, Assumptions (Detail)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]      
Expected term (years) 5 years 8 months 12 days 4 years 2 months 12 days 5 years 1 month 6 days
Risk-free interest rate 1.80% 1.30% 1.20%
Expected volatility 75.20% 78.70% 89.30%
Expected dividend yield 0.00% 0.00% 0.00%