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Stockholders' Equity - Summary of Stock Option Outstanding (Detail) - $ / shares
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Equity [Abstract]      
Option Outstanding - Range of Exercise Prices, Lower Limit $ 1.17 $ 1.17  
Option Outstanding - Range of Exercise Prices, Upper Limit $ 23.20 $ 26.00  
Option Outstanding - Number of Shares 2,445,453 1,773,066 1,389,816
Option Outstanding - Weighted-Average Remaining Contractual Life 7 years 7 months 6 days 6 years 10 months 25 days  
Option Outstanding - Weighted Average Exercise Price $ 3.37 $ 7.02 $ 8.39
Option Exercisable 1,209,087 999,999  
Option Exercisable - Weighted Average Exercise Price $ 4.47 $ 10.05