| Stock Option Plans (Tables)
 | 12 Months Ended | 
| Dec. 31, 2019 | 
|---|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  | 
| Schedule of Weighted-average Assumptions to Estimate the Fair Value of the Options Granted | We used the following weighted-average
assumptions to estimate the fair value of the options granted for the years indicated:   
    |  |  | For the years ended December 31, |  |  
    |  |  | 2019 |  |  | 2018 |  |  | 2017 |  |  
    | Expected volatility |  |  | 108 | % |  |  | 109 | % |  |  | 111 | % |  
    | Expected term |  |  | 5.1 years |  |  |  | 5 years |  |  |  | 5 years |  |  
    | Risk-free interest rate |  |  | 2.21 | % |  |  | 2.62 | % |  |  | 1.81 | % |  
    | Expected dividend yield |  |  | 0.00 | % |  |  | 0.00 | % |  |  | 0.00 | % |  | 
| 2015 Equity Incentive Plan [Member] |  | 
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  | 
| Schedule of Options Activity | Summarized information for the 2015
Equity Incentive Plan is as follows:   
    |  |  | Options |  |  | Weighted- average
 exercise
 price
 |  |  
    | Outstanding options at January 1, 2017 |  |  | 4,443,000 |  |  | $ | 4.94 |  |  
    | Granted, fair value of $11.35 per share |  |  | 1,077,000 |  |  |  | 14.31 |  |  
    | Exercised |  |  | (81,719 | ) |  |  | 4.22 |  |  
    | Expired/forfeited |  |  | (325,314 | ) |  |  | 5.52 |  |  
    | Outstanding options at December 31, 2017 |  |  | 5,112,967 |  |  | $ | 9.07 |  |  
    |  |  |  |  |  |  |  |  |  |  
    | Granted, fair value of $10.23 per share |  |  | 1,497,300 |  |  | $ | 12.95 |  |  
    | Exercised |  |  | (360,853 | ) |  |  | 6.22 |  |  
    | Expired/forfeited |  |  | (724,009 | ) |  |  | 10.65 |  |  
    | Outstanding options at December 31, 2018 |  |  | 5,525,405 |  |  | $ | 8.08 |  |  
    |  |  |  |  |  |  |  |  |  |  
    | Granted, fair value of $5.14 per share |  |  | 1,490,490 |  |  | $ | 6.53 |  |  
    | Exercised |  |  | (303,129 | ) |  |  | 3.20 |  |  
    | Expired/forfeited |  |  | (917,371 | ) |  |  | 7.95 |  |  
    | Outstanding options at December 31, 2019 |  |  | 5,795,395 |  |  | $ | 7.96 |  |  
    |  |  |  |  |  |  |  |  |  |  
    | Non-vested options at December 31, 2017 |  |  | 2,641,832 |  |  | $ | 8.21 |  |  
    | Non-vested options at December 31, 2018 |  |  | 2,355,719 |  |  | $ | 10.41 |  |  
    | Non-vested options at December 31, 2019 |  |  | 2,342,706 |  |  | $ | 8.78 |  |  | 
| Schedule of Options Outstanding and Exercisable | Further information regarding options
outstanding under the 2015 Equity Incentive Plan at December 31, 2019 is summarized below:   
    |  |  |  |  |  |  |  |  |  | Weighted-average |  |  |  |  |  | Weighted-average |  |  
    | Range of exercise prices |  |  | Number of options outstanding |  |  | Remaining life in years |  |  | Exercise price |  |  | Number of options exercisable |  |  | Remaining life in years |  |  | Exercise price |  |  
    | $ | 2.26 |  |  | $ | 5.44 |  |  |  | 1,989,150 |  |  |  | 7.0 |  |  | $ | 3.66 |  |  |  | 1,462,346 |  |  |  | 6.5 |  |  | $ | 3.46 |  |  
    |  | 5.90 |  |  |  | 9.23 |  |  |  | 2,425,240 |  |  |  | 7.6 |  |  |  | 7.35 |  |  |  | 1,253,189 |  |  |  | 6.2 |  |  |  | 7.32 |  |  
    |  | 11.43 |  |  |  | 14.45 |  |  |  | 456,619 |  |  |  | 8.5 |  |  |  | 13.49 |  |  |  | 204,025 |  |  |  | 8.4 |  |  |  | 13.56 |  |  
    |  | 15.25 |  |  |  | 17.30 |  |  |  | 924,386 |  |  |  | 8.0 |  |  |  | 16.09 |  |  |  | 533,129 |  |  |  | 8.0 |  |  |  | 16.07 |  |  
    |  |  |  |  |  |  |  |  |  | 5,795,395 |  |  |  |  |  |  |  |  |  |  |  | 3,452,689 |  |  |  |  |  |  |  |  |  |  | 
| 2005 Equity Incentive Plan [Member] |  | 
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  | 
| Schedule of Options Activity | Summarized information for the 2005
Equity Incentive Plan is as follows:   
    |  |  | Options |  |  | Weighted- average
 exercise
 price
 |  |  
    | Outstanding options at January 1, 2017 |  |  | 328,560 |  |  | $ | 14.57 |  |  
    | Expired/forfeited |  |  | (11,800 | ) |  |  | 21.53 |  |  
    | Outstanding options at December 31, 2017 |  |  | 316,760 |  |  | $ | 14.31 |  |  
    |  |  |  |  |  |  |  |  |  |  
    | Expired/forfeited |  |  | (360 | ) |  |  | 150.00 |  |  
    | Outstanding options at December 31, 2018 |  |  | 316,400 |  |  | $ | 14.15 |  |  
    |  |  |  |  |  |  |  |  |  |  
    | Expired/forfeited |  |  | (56,400 | ) |  |  | 19.75 |  |  
    | Outstanding options at December 31, 2019 |  |  | 260,000 |  |  | $ | 12.94 |  |  | 
| Schedule of Options Outstanding and Exercisable | Further information regarding options
outstanding under the 2005 Equity Incentive Plan at December 31, 2019 is summarized below:   
    |  |  |  |  |  |  |  |  |  | Weighted-average |  |  |  |  |  | Weighted-average |  |  
    | Range of exercise prices |  |  | Number of options outstanding |  |  | Remaining life in years |  |  | Exercise price |  |  | Number of options exercisable |  |  | Remaining life in years |  |  | Exercise price |  |  
    | $ | 3.25 |  |  | $ | 3.25 |  |  |  | 120,000 |  |  |  | 0.1 |  |  | $ | 3.25 |  |  |  | 120,000 |  |  |  | 0.1 |  |  | $ | 3.25 |  |  
    |  | 11.50 |  |  |  | 30.50 |  |  |  | 136,100 |  |  |  | 4.1 |  |  |  | 18.48 |  |  |  | 136,100 |  |  |  | 4.1 |  |  |  | 18.48 |  |  
    |  | 113.50 |  |  |  | 122.50 |  |  |  | 3,900 |  |  |  | 0.9 |  |  |  | 117.65 |  |  |  | 3,900 |  |  |  | 0.9 |  |  |  | 117.65 |  |  
    |  |  |  |  |  |  |  |  |  | 260,000 |  |  |  |  |  |  |  |  |  |  |  | 260,000 |  |  |  |  |  |  |  |  |  |  |