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Stock-Based Compensation - Assumptions Used to Estimate Fair Value of Stock Options (Detail)
3 Months Ended 6 Months Ended
Jun. 30, 2019
Jun. 30, 2019
Share-based Payment Arrangement [Abstract]    
Risk-free interest rate 2.10% 2.10%
Expected term (in years) 2 years 7 months 6 days 2 years 7 months 6 days
Expected volatility 55.00% 55.00%
Expected dividend yield 0.00% 0.00%