Capital Stock - Common stock activity (Details) - USD ($)
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Jan. 28, 2016
Common stock activity        
Balances at the beginning 11,175,125      
Balances at the end 10,722,675 11,175,125    
Purchases of treasury stock $ 9,969,468      
Common Stock        
Common stock activity        
Balances at the beginning 11,175,125 10,814,650 7,000,000  
Issued pursuant to initial public offering     2,318,400  
Conversion of preferred stock     1,400,000  
Option exercises 111,763 345,475 96,250  
Warrant exercises 5,000 15,000    
Purchase and retirement of treasury stock (569,213)      
Balances at the end 10,722,675 11,175,125 10,814,650  
Purchases of treasury stock $ 9,969,468      
Maximum        
Common stock activity        
Repurchase of the stock       $ 10,000,000