Fair Value of Stock Options Assumptions Using Black-Scholes Option Valuation Model (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Risk-free interest rate, Minimum	0.89%	0.36%	0.50%	0.36%
Risk-free interest rate, Maximum	0.96%	0.39%	1.15%	1.68%
Expected volatility, Minimum	72.53%	73.59%	72.53%	71.11%
Expected volatility, Maximum	72.84%	74.18%	74.80%	74.18%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Maximum [Member]
Expected life in years	6 years 3 months	6 years 3 months	6 years 3 months	6 years 3 months
Minimum [Member]
Expected life in years	6 years	5 years 9 months	5 years 6 months	5 years 9 months