Annual report pursuant to Section 13 and 15(d)

Stock Option Plans (Assumptions Used To Compute The Fair Value Of Stock Options) (Detail)

v3.19.1
Stock Option Plans (Assumptions Used To Compute The Fair Value Of Stock Options) (Detail) - USD ($)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Assumptions for Black-Scholes:      
Expected term in years     7 years 10 months 24 days
Value of options granted:      
Number of options granted 330,500 534,500 116,750
Weighted average fair value per share $ 5.01 $ 5.24 $ 5.73
Fair value of options issued $ 1,655,390 $ 2,803,329 $ 669,435
Minimum [Member]      
Assumptions for Black-Scholes:      
Expected term in years 6 years 4 months 24 days 6 years 6 months  
Volatility 108.90% 122.80% 103.60%
Risk-free interest rate 2.95% 1.98% 1.27%
Maximum [Member]      
Assumptions for Black-Scholes:      
Expected term in years 6 years 7 months 6 days 6 years 9 months 18 days  
Volatility 119.40% 133.00% 109.70%
Risk-free interest rate 3.08% 2.30% 1.68%