Stock Options: (Details 1) - $ / shares
6 Months Ended 12 Months Ended
Jun. 30, 2016
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]        
Stock Options Outstanding, Number of Shares 8,832,534 8,582,952 7,769,202 6,249,952
Stock Options Outstanding, Weighted Avg. Contractual Life (years) 7 years 3 months 18 days 7 years 6 months    
Weighted Avg. Exercise Price $ 1.3 $ 1.32 $ 1.40 $ 1.48
Stock Options Exercisable, Number of Shares 6,181,229 5,776,716    
Stock Options Exercisable, Weighted Avg. Exercise Price $ 1.39 $ 1.41    
Exercise Price Range One [Member]        
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]        
Range of Exercise Prices, Lower Range Limit 0.01 0.01    
Range of Exercise Prices, Upper Range Limit $ 0.71 $ 0.71    
Stock Options Outstanding, Number of Shares 1,078,082 750,000    
Stock Options Outstanding, Weighted Avg. Contractual Life (years) 9 years 1 month 10 days 8 years 10 months 10 days    
Weighted Avg. Exercise Price $ 0.61 $ 0.61    
Stock Options Exercisable, Number of Shares 665,582 528,082    
Stock Options Exercisable, Weighted Avg. Exercise Price $ 0.61 $ 0.61    
Exercise Price Range Two [Member]        
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]        
Range of Exercise Prices, Lower Range Limit 0.80 0.80    
Range of Exercise Prices, Upper Range Limit $ 1.00 $ 1.00    
Stock Options Outstanding, Number of Shares 3,062,048 3,120,548    
Stock Options Outstanding, Weighted Avg. Contractual Life (years) 7 years 11 months 5 days 8 years 5 months 8 days    
Weighted Avg. Exercise Price $ 0.93 $ 0.93    
Stock Options Exercisable, Number of Shares 1,478,024 1,343,394    
Stock Options Exercisable, Weighted Avg. Exercise Price $ 0.96 $ 0.96    
Exercise Price Range Three [Member]        
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]        
Range of Exercise Prices, Lower Range Limit 1.11 1.11    
Range of Exercise Prices, Upper Range Limit $ 1.55 $ 1.55    
Stock Options Outstanding, Number of Shares 1,120,000 1,120,000    
Stock Options Outstanding, Weighted Avg. Contractual Life (years) 7 years 8 months 26 days 8 years 2 months 26 days    
Weighted Avg. Exercise Price $ 1.32 $ 1.32    
Stock Options Exercisable, Number of Shares 842,438 783,589    
Stock Options Exercisable, Weighted Avg. Exercise Price $ 1.25 $ 1.23    
Exercise Price Range Four [Member]        
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]        
Range of Exercise Prices, Lower Range Limit 1.64 1.64    
Range of Exercise Prices, Upper Range Limit $ 2.22 $ 2.22    
Stock Options Outstanding, Number of Shares 3,572,404 3,592,404    
Stock Options Outstanding, Weighted Avg. Contractual Life (years) 7 years 3 months 18 days 7 years 9 months 18 days    
Weighted Avg. Exercise Price $ 1.82 $ 1.82    
Stock Options Exercisable, Number of Shares 3,195,185 3,121,651    
Stock Options Exercisable, Weighted Avg. Exercise Price $ 1.79 $ 1.78