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Stock-Based Compensation - Summary of Weighted-Average Assumptions Used in the Black-Scholes Option Pricing Model to Determine the Fair Value of the Non-Employee Stock Option Grants (Detail)
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Share-based Goods and Nonemployee Services Transaction [Abstract]    
Risk-free interest rate 1.57% 1.79%
Expected volatility 63.50% 63.20%
Expected term (in years) 7 years 6 years 1 month 28 days
Expected dividend yield 0.00% 0.00%